Stuttering Problem - Everyone stumped...

[Stang70Fastback]

This is something that I've asked about on two car forums (one is legacygt.com) AND my local Subaru dealership spend an ENTIRE DAY diagnosing with no solution found. I cannot possibly imagine it's something terribly complicated, but no-one seems to know the answer. I'm just going to copy this from the other forums because I'm getting tired of re-writing everything. Hopefully someone here can shed some light on the issue.

---copied from legacygt.com---

I guess my question is, is there anyone here who could maybe give me any ideas as to what the issue could be? The problem is that at LOW RPMs with light throttle (up to about 1500 RPM) the engine goes kind of like vroom... vroom... vroom (like almost stalling and then kicking up again, over and over) with the car lurching until you get above 1500 RPM. It does not happen when you first start the car (cold engine) but only after it's been warmed up. It can be pretty nasty in lurching the car forward. I guess the strangest part is the fact that sometimes it does it pretty badly, but the Check Engine light NEVER comes on, which is annoying to say the least.

Idle is not the problem. It idles fine, it's as soon as you give it a bit of gas, only like I said under 1500 RPM that it starts to stutter and rev and stutter and rev...

We just paid $350 for a new oxygen sensor which did NOT fix the issue, and now they want to start it off with a $150 diagnostic session, which might actually cost more than that depending on how long it takes to pinpoint the issue. I'm not going to do that on a car with 211,000 miles.

---copied from CCVT forums---

I have a problem with my car that's been going on for months now, gradually getting worse. It only happens when the car is warmed up, and not 100% of the time. What I get is that if I lightly press the throttle - like really lightly (think stop and go traffic acceleration) up to about 1500 RPM, the engine will repeatedly feel like its going to stall and then surge and stall and surge, and the car bucks forward in 1-second intervals. It's extremely aggravating (and a bit dangerous) in traffic, and even more annoying when I just want to move the car forward without mashing the gas pedal. If you're ever behind me and it looks like I've got a manual and I dunno how to work the clutch, that's what the problem is, lol. I've had it into Subaru twice for diagnostics and they can't at all figure out what it is. Even had me pay $350 to replace an O2 sensor which didn't solve the problem.

It's violent enough (like really pretty bad) that you'd think it would throw a code or two (I have an OBDII scanner hooked up to the carputer) but it hasn't said ANYTHING. If anyone has any possible ideas as to what it might be, let me know. They said they'd checked the air filter and the fuel filter to no avail. I'm thinking maybe it's a fuel-supply problem (like maybe the fuel pump mot giving enough fuel when I only press the gas a little. I really want to get this resolved, but I'm not going to keep paying to have people come up with no answer... The guy who looked at it at Flemington Subaru is something like Subaru's 3rd best mechanic in the country or something like that, so I've kind of lost hope at this point, lol.

It's hard to explain. I've had experience with the car misfiring, and aside from the fact that even the SLIGHTEST misfire causes the CEL to go berserk (which it doesn't in this case) it doesn't really feel like a cylinder is firing at the wrong time. Usually you can feel the engine kick-back when that happens. This just feels more like it simply dies.

They also said they checked the spark plugs (and on this car, with a flat boxer engine, its not at all easy to do.) AND they checked the coil pack.

Unless he was lying about all that stuff. Or unless I'm completely making all of this up, but I remember him going over the list of things they looked at. I mean they spent a good few HOURS on the thing.

Also, I see people are arguing about the O2 sensors. I would like to add that they replaced it because the sensor was occasionally reading 0V when they were looking at it. When that didn't fix the problem, they said that BOTH O2 sensors had been reading 0V occasionally, so that it might be the rear one, but at that point I just took the car back.

---

That's all I can say about the problem. Hopefully someone here might have an idea?

[1996Battlewagon]

Looks like you need a new mechanic.

Your symptoms do sound like you have a misfire; but you said no code so we can toss that out the window (for now). Do you have an aftermarket intake and/or your snorkus removed? Because sometimes, these can cause and/or make MAF hesitation problems to be worse. You might want to check the MAF. Here:
viewtopic.php?f=11&t=11459 (https://sl-i.net/FORUM/viewtopic.php?f=11&t=11459)

That might help, maybe.

[Stang70Fastback]

Everything is stock. I just replaced the air filter, which was pretty dirty and at first it seemed to help but maybe not. The problem is definitely still there, I just thought it was a bit better, but I think it's just me.

The mechanic who looked at it is their top mechanic! I'll check out that link and see what I can do.

[Plays_with_Toys]

Firstly, never spend more than $80 on your O2 sensor. You can buy bosch equivalent O2 sensors for $50-60 front and rear. If you want to proceed with the rear replacement go this route.

First things first: What year? What model? What transmission? How many miles? Original owner or not?

The first thing I thought of was along your intake tract. I'd buy some MAF cleaner and clean the sensor. You can buy a can of this stuff for like $5 at any auto parts store. It will be called Mass air flow sensor cleaner. It's different from the electrical contact cleaner. The other thing I was thinking is something screwy with the throttle position sensor. Is that something you can check with the carputer? The voltage at the TPS when the bucking happens?

[Stang70Fastback]

Firstly, never spend more than $80 on your O2 sensor. You can buy bosch equivalent O2 sensors for $50-60 front and rear. If you want to proceed with the rear replacement go this route.

First things first: What year? What model? What transmission? How many miles? Original owner or not?

The first thing I thought of was along your intake tract. I'd buy some MAF cleaner and clean the sensor. You can buy a can of this stuff for like $5 at any auto parts store. It will be called Mass air flow sensor cleaner. It's different from the electrical contact cleaner. The other thing I was thinking is something screwy with the throttle position sensor. Is that something you can check with the carputer? The voltage at the TPS when the bucking happens?

To answer your questions:

1998 Subaru Legacy Outback Limited - 4EAT (still original - no overhaul or anything!) - 222k miles - parents bought the car in 2000 used with something like 20 or 40k miles on it. So we've pretty much owned the car for most of it's life. I've had the car for about 30-40k miles. The head gaskets were replaced somewhere around 30-40k miles ago as well... maybe even a bit more, I don't quite remember. Temp needle was pinned quite a few times as a result (we drove it for months before fixing it.) Engine was deemed fine (heads even sent in to make sure they weren't warped) and gaskets replaced. Thermostat failed about a year later (probably result of all the overheating) and that was replaced. The car was running fine (fine being what it is for a car with this many miles) until this started happening. I should mention it wasn't a sudden onset. It gradually started happening - barely noticeable at first - and then deteriorated to what it is now, where it almost sounds like it will stall. What I'm going to try to do is take a video of the car doing it so you guys can see/hear, which might help diagnose the problem.

I will take a look at the TPS reading (I cannot read the voltage, but I can read the position) and see if it jumps around, but I'm fairly certain that's not the issue. As for cleaning the MAF, if that's the thing right behind the air filter, I should mention that I was actually looking at it not three days ago (through the little grate - I didn't actually take it out) and that entire assembly, and everything around it, looks brand spanking new, so I don't think it's dirt or anything.

[Okin DaVanh]

Might sound a bit far fetched, but did you swap the fuel filter too?

[Plays_with_Toys]

The MAF is a heated resistor type element, so it wouldn't take much to offset its readings. Essentially the wire is heated, and as air passes it, the amount it is cooled changes the voltage to tell the engine how much air is entering.

EDIT: oh, and the other thing needing to be done is check for vacuum leaks, though a little less likely... You'd probably be experiencing idle problems if you had a vacuum leak.

[99gtlimited]

I'm gonna say you need to clean or replace your MAF. That's my guess, seems likely with our cars.

[Stang70Fastback]

I'm gonna say you need to clean or replace your MAF. That's my guess, seems likely with our cars.

Assuming I wanted to do that, and cleaning it didn't work, how expensive would it be to replace, and is this something I could do myself? (I dunno much about this kind of stuff... I don't work on my own car, though I'm willing to learn.)

I've uploaded a video to youtube. The car had only been driven for a short period, so the problem hadn't fully developed. You can kind of hear it, but maybe it isn't as apparent if you haven't heard it in person, I rev the engine, then it stutters, almost stalls, then picks up again and the car jerks forward over and over. Here it wasn't too violent and wasn't doing it too repeatedly but you can still hear it.

http://www.youtube.com/watch?v=PFMREeE5TR8 (If you watch the video in HIGH QUALITY (bottom right of video) you hear it a LOT better...)

[99gtlimited]

both the cleaning and replacement are very straightforward and easy even for the most inexperienced wrench monkey...

also have you checked your plugs/replaced them recently, wouldn't hurt to give that a look too, symptoms could be duet to incomplete combustion (possibly caused by timing too)

[Stang70Fastback]

both the cleaning and replacement are very straightforward and easy even for the most inexperienced wrench monkey

Hmmm - well maybe I'll take it out and give it a blast of compressed air or that other stuff. I mean is it basically just like something you unscrew? Lol. I can't **** up my car - not now - it's too cold to take the bus to class! Plus, we're getting a snow and ice storm Tuesday - and I need to have it working by then so I can go... inspect... the road conditions :D

[T_F_E]

I wouldnt go to crazy with compressed air if your talkin from a compressor that could cause some damage.

[99gtlimited]

DO NOT USE COMPRESSED AIR!!! this is a very sensitive sensor, they sell a specific product for cleaning MAF sensors, i suggest you find some of that. As far as removal it's really straight forward, unclip the plug, and unbolt, or unscrew and remove.

[Stang70Fastback]

Just grabbed a bottle from the local store. I realize how easy this will be now, lol. Am I correct in reading that you just spray it on and let it try, and that will clean it? You don't actually touch it at any point.

[T_F_E]

That should be correct, do not touch it as said before it is extremely sensitive

[Stang70Fastback]

That should be correct, do not touch it as said before it is extremely sensitive

I'm tempted to go out and do it now even though its dark cause it sounds like a 9 minute job... lol.

[99gtlimited]

yeah go for it, pull the MAF out and give it a good spraying, then let it dry and put it back in. This obviously won't help the MAF if the sensor itself is bad. Good luck!

[Stang70Fastback]

Done and done. First I took off that while-plastic colored thing (where you unplug the MAF) and unscrewed that, thinking that was it. When it came off leaving just those prongs I got worried. So I put it back on, and just took the whole thing off and sprayed into the tube (probably what I was supposed to do.) Let it dry, put everything back together, took it out for a drive... same thing.

I just unplugged the battery. I'm going to let it drain for the next 12 hours before I have to go to class at 7:30 tomorrow morning. Maybe resetting the ECU will do it. Other than that, I have no idea. I was watching the MAF readings on my carputer, and everything seemed fairly normal (e.g. the values didn't jump around and changed with engine RPM). I don't think the MAF is the issue...

[sexystover]

anyone think it could be the tranny causing the problem?

[Okin DaVanh]

also have you checked your plugs/replaced them recently, wouldn't hurt to give that a look too, symptoms could be duet to incomplete combustion (possibly caused by timing too)


I know... after seeing/hearing the video I can't help but to say the same thing. It sounds almost as if 1 of the plugs aren't in all the way or a bad plug wire.... :smt102

[99gtlimited]

It doesn't take that long to reset the ECU you only need to leave it unplugged for about 60 seconds, pushing the brake pedal discharges the system really fast.

[Stang70Fastback]

While these are all possibilities, why would this only occur at less than 5 mph, on light throttle, at less than 1200 RPM? It doesn't happen in any other scenario. To give you an example, the best way to have it continually do it is to creep up a hill so that the car doesn't actually pick up speed but crawls along at like 2-3 mph and it will jerk forward, stumble, jerk, etc... If I put it in second gear, and accelerate from a stop, it seems to happen less. Would a loose plug wire only cause it to happen in that situation?

Maybe it is the transmission. I say that only because its the original tranny with 222k miles on it. Never been overhauled or anything. It's starting to show it's age (shift from 1st to 2nd is a slam-jerk most of the time cause I think the synchros are going) and when it upshifts coasting down a hill it slows the car down sometimes relatively sharply before getting into higher gear (almost feels like a downshift first.) It's sad because this car is in relatively decent shape, but this problem really sucks. In stop and go traffic it's a nightmare because it's embarrassing (makes it look like I can't shift and have a manual) and hard to not run into the car in front, or even maintain a steady 2-3 mph crawl without jerking about.

And thanks to everyone who's trying to help me out with this. I'm desperate for a solution.

EDIT: In that case, I'll go back down, press the brake for a minute or two, and plug it back in and go for one last drive tonight and see what's what.

[T_F_E]

its auto right? if so my new guess is torque converter

[Stang70Fastback]

its auto right? if so my new guess is torque converter

Ahhhh now THAT'S INTERESTING! New story:

Brought the car in about a year ago for an issue I'm still having to this day. Sometimes when I accelerate, when I first tap the throttle (again lightly - maybe it does it if I go WOT but it's so short it isn't noticeable) but when I lightly tap the throttle (say 5-10%) the engine will literally cut out for a second and the RPMs will drop and then it will rev up. This is NOT the same issue as above, it just sound like it cuts out for a second and then comes back (like a split second) anyway, I brought it to Subaru and they told me it was the torque converter causing the problem. I believe the reason we didn't fix it was a.) It was just a nuisance, but a real problem, and b.) it would be expensive.

So it's interesting you bring that out because, according to the one dealership, I need a new one of those.

[T_F_E]

OK i am now 90 percent sure this is your problem, a torque converter is the clutch for an automatic car, if you are going to replace this you might as well do the whole transmission because of the high mileage and the tranny being dropped anyway.

[Stang70Fastback]

OK i am now 90 percent sure this is your problem, a torque converter is the clutch for an automatic car, if you are going to replace this you might as well do the whole transmission because of the high mileage and the tranny being dropped anyway.

Ah. Well in that case I guess I'll have to live with it. Can't afford that kind of stuff :(

I'm pretty sure I'm going to be driving this car until it dies... lol.

[T_F_E]

OK i am now 90 percent sure this is your problem, a torque converter is the clutch for an automatic car, if you are going to replace this you might as well do the whole transmission because of the high mileage and the tranny being dropped anyway.

Ah. Well in that case I guess I'll have to live with it. Can't afford that kind of stuff :(

I'm pretty sure I'm going to be driving this car until it dies... lol.

It seems you have a lot of people around you on here it may just take a trip to a junk yard and a case of beer and you could have the problem fixed.

[Stang70Fastback]

It seems you have a lot of people around you on here it may just take a trip to a junk yard and a case of beer and you could have the problem fixed.

Yeah. We'll have to see what's what here. This sounds like it really is the problem and if I can get people to help me out here since I don't know anything about this stuff, maybe I can rustle up some $$$.

Thanks for the help!

[ScaryFatKidGT]

throttle position sensor or fuel pump going out/starting to go out?

[T_F_E]

Anytime :smt023

[impreza_GC8]

Torque converter is a very good guess and from watching that vid it almost looks like someone who doesn't know how to drive a manual trans car is nearly killing it from a stop.
Also, from watching the vid, let me say that your car is in beautiful condition for its age. That paint is gorgeous. I wish I had your shell to drop my engine and drivetrain into.

[Stang70Fastback]

Torque converter is a very good guess and from watching that vid it almost looks like someone who doesn't know how to drive a manual trans car is nearly killing it from a stop.

Exactly, lol. I feel an idiot when I'm driving it. I wonder how much a torque converter/tranny in good nick would cost me. Off to the classifieds!


Also, from watching the vid, let me say that your car is in beautiful condition for its age. That paint is gorgeous. I wish I had your shell to drop my engine and drivetrain into.

You're not the first to say that. Once you get close you can see quite a few pretty bad issues, but it is true that where it isn't scuffed it does have a nice deep color and shine. I don't understand that either, because it's originally a NJ car and us usually covered in salt in the winder and out in the sun a lot in the summer. I guess I got a good one, lol.

[Plays_with_Toys]

Call me crazy, but I don't see how a torque converter can cause the car to limp like that when he says this:


Sometimes when I accelerate, when I first tap the throttle (again lightly - maybe it does it if I go WOT but it's so short it isn't noticeable) but when I lightly tap the throttle (say 5-10%) the engine will literally cut out for a second and the RPMs will drop and then it will rev up. This is NOT the same issue as above

Sounds like a fuel delivery/combustion issue. And contrary to what he says, it sounds like it is exactly the same problem as above.

Ok, since you have said a few things which point to not being very mechanically inclined lets cover the bases.

1. Spark plugs (NGK or Denso, nothing else, gapped correctly)
2. Plug Wires
3. Fuel Filter
4. Air Filter
5. PCV valve

These are the things that are replaced in a routine tune up. If these have not been replaced, then you certainly haven't taken the diagnosis, well... anywhere. You said that things were checked. I don't know how you can check a fuel filter, sniff it? And did they pull the plug wires and spark it against the frame to see if they were igniting or what? Not entirely sure how the mechanics "checked it" especially when you said you turned down the diagnosis service, which means you might have turned down them ever looking at the car. That wasn't very clear.

If it were the torque converter acting up, it is binding upon start up, which is causing the RPMs to drop down as the engine struggles to move. The other way the torque converter/transmission would act up is the engine would rev up with no real response. The reason is that transmission fluid is the working fluid in the system. The torque converter is used all the time in delivering power and uses transmission fluid to transfer torque through its centripetal force. I would think a torque converter issue would show itself through your gas mileage and in higher speeds. What is your gas mileage (city/hwy)?

That's like people jumping on the headgasket bandwagon everytime one of these things over heats. They jump in saying this must be the problem because they haven't gone through the steps to figure it out. $1000-2000 later their car overheats again because they never fixed the real problem in the first place.

[Stang70Fastback]

Alright, well you took the time to deliver a very thorough post, so I'll try to reply thoroughly :)


Call me crazy, but I don't see how a torque converter can cause the car to limp like that when he says this:


Sometimes when I accelerate, when I first tap the throttle (again lightly - maybe it does it if I go WOT but it's so short it isn't noticeable) but when I lightly tap the throttle (say 5-10%) the engine will literally cut out for a second and the RPMs will drop and then it will rev up. This is NOT the same issue as above

Sounds like a fuel delivery/combustion issue. And contrary to what he says, it sounds like it is exactly the same problem as above.

I see what you're saying, but first off, these are two different issues. The problem where the engine seems to cut out is completely independent of the stuttering issue (e.g. they can happen exclusively or both at the same time.) ALSO, you're saying it's the clutch bogging the engine down, but I forgot to mention the very important point that this will happen in park, or neutral. When it happens in gear it feels more like the engine cuts out than the car bogging it down (e.g. no movement.)


Ok, since you have said a few things which point to not being very mechanically inclined lets cover the bases.

1. Spark plugs (NGK or Denso, nothing else, gapped correctly)
2. Plug Wires
3. Fuel Filter
4. Air Filter
5. PCV valve

These are the things that are replaced in a routine tune up. If these have not been replaced, then you certainly haven't taken the diagnosis, well... anywhere. You said that things were checked. I don't know how you can check a fuel filter, sniff it? And did they pull the plug wires and spark it against the frame to see if they were igniting or what? Not entirely sure how the mechanics "checked it" especially when you said you turned down the diagnosis service, which means you might have turned down them ever looking at the car. That wasn't very clear.

I should have checked the post I copied. It does say that I turned down the diagnostic because they wanted to charge me for it, but what ended up happening was they took the car for the day free of charge to try and find the issue. Their best mechanic worked on it. Unfortunately, I do not know exactly what he looked at. I'm fairly certain that he checked the spark plugs because I remember talking about that but I'm not certain. The plugs were replaced not-too-long-ago I believe (at least when the head gaskets were done which was somewhere in the order of 40k ago.) I did replace the air filter a week ago to no avail. I wouldn't know anything about the plug wires, the fuel filter and the PCV valve. He might have checked all of these, he might not have, I don't really know.


If it were the torque converter acting up, it is binding upon start up, which is causing the RPMs to drop down as the engine struggles to move. The other way the torque converter/transmission would act up is the engine would rev up with no real response. The reason is that transmission fluid is the working fluid in the system. The torque converter is used all the time in delivering power and uses transmission fluid to transfer torque through its centripetal force. I would think a torque converter issue would show itself through your gas mileage and in higher speeds. What is your gas mileage (city/hwy)?

Yeah, I don't have any problems with the engine revving freely (I guess a slipping clutch issue is what you're talking about) and I get about 400 miles to a tank on drives to and from NJ, so gas mileage is perfect.


That's like people jumping on the headgasket bandwagon everytime one of these things over heats. They jump in saying this must be the problem because they haven't gone through the steps to figure it out. $1000-2000 later their car overheats again because they never fixed the real problem in the first place.

I know what you mean. Here's another tidbit that may or may not be relevant, I don't know. Another issue I have is when I come to a stop, I usually have to knock the car into neutral otherwise the whole car starts shuddering and it feels as if the car really wants to go forward, as if the clutch, or torque converter - whatever you want to call it - isn't disengaging all the way. When I knock it into neutral, the revs go up like by about 100 RPM and then settle back down. Maybe that's a sign the torque converter is acting up?

[SubaGlue]

I agree with others: Spark plugs / wires.

My Leggy had a misfire problem and it sputtered strangely like that. after i got new plugs and wires it ran fine

Thats my guess :-?

[LegacyRob]

Try putting some of that transmission stop slip stuff in your tranny to see if that helps. If it makes a difference then maybe your on to something.

[Huffer]

Try putting some of that transmission stop slip stuff in your tranny to see if that helps. If it makes a difference then maybe your on to something.

Not a good idea. The only additive I would put in a 4EAT would be Lubegard ATF Protectant.

[99gtlimited]

for the bogging issue i'm thinking throttle position sensor

[Stang70Fastback]

I would absolutely love to have everyone here take turns and try their recommendations, lol. There are so many different opinions!

Someone else was telling me it might even be the cats...

[decke48]

doesnt its go hard into gear?
pluged cat will make the car bog down and sputter

[Brockley]

It seems you have a lot of people around you on here it may just take a trip to a junk yard and a case of beer and you could have the problem fixed.

Yeah. We'll have to see what's what here. This sounds like it really is the problem and if I can get people to help me out here since I don't know anything about this stuff, maybe I can rustle up some $$$.

Thanks for the help!


Yea man, Me and Mike can both come help sometime, we did the tranny on my GT, plus worked on swapping two WRX-RS's so its fairly easy at this point.

Did you check all the vac. lines running into the intake? I know when I had mine apart, it stuttered really bad, but I never drove it, so not sure if it would have gone away like yours.

Or better yet, lets just find me a Postal wagon now, and you can get the parts you need for cheap.. lol

Brock

[Stang70Fastback]

Just a new development. Sitting around outside waiting to pick up my friend (car warmed up and idling.) All of a sudden I started to hear the idle dropping a hair and then going back up again and then dropping again. I thought "ohhh no..." and sure enough it started getting worse until it was stuttering just like the problem I've been having with light throttle application. It got worse and worse over the next like 30 seconds to a minute to the point where I thought it would stall. It would drop down to ALMOST stalling and then shoot back up and then stall again. If you plotted the RPMs it would look like a sinusoidal curve getting bigger and bigger. And then, for the first time ever, it actually did stall. It wasn't violent. It just kind of died almost as if I'd turned it off. That's NEVER happened with this stuttering problem, but then again it's never done it idling either. So I started it up, it ran for 30 seconds, then did the same thing and stalled again. So before turning it on again, I booted up my carputer, plugged it in, started the car, connected the OBD-II and monitored the MAF sensor, intake manifold pressure, fuel loop status and one or two other things hoping to see something when it happened again, but of course the car ran like a top after that.

So I still dunno what's going on but it's obviously getting worse :(

And STILL no FREAKING CEL.

[Huffer]

I'm going to say carbon build up in the intake manifold/throttle body and an unclean Idle Air Control Valve. I have the same issue with my car, it's a manual though. But when idling, my car will idle like a race car. Up/down.

I just haven't made the time to clean the TB and the IACV.

[Stang70Fastback]

Today I stopped to fill my tires up with air, and left the car running while I did that. Got in, went to pull out of the Exxon station, as I went to turn the wheel to turn onto the road, I couldn't turn it and realized that for the second or two when i coasted into the street, the car had stalled. Had to LUG the wheel over, and pulled the car into a parking lot. This has gotten to the point now of being dangerous because the car is going to start stalling randomly whenever I'm off the gas. Started it up and it did it three more times, and then was fine again. This time I watched the MAF reading (which reads .5, .6, .4 depending on where it was in the RPM range) and not once did it fluctuate to something ridiculous, so I think the MAF is fine.

[Huffer]

Could be the neutral switch on the tranny then - if it's fritzing out it can send a signal to the tranny that it's in neutral...

Kinda clutching at straws here - but even if the MAF is registering the right voltage, it could be something else further down the line like a vac. leak.

[evolegacy]

other than his most recents posts, i have had the same issue, including a couple stalls but my issue was fixed when i changed my plugs, wires, and coil, but stupid me bought cheapos and now its acting up again, hehe.

I'd check the vac lines as well, i just checked mine tonight because of a CEL P0106 (MAP/MAF malfunction: dirty/defective [blame run from MA to CT ^_^"]), and they were pretty bad, going to just replace them all with this upcoming paycheck.

[Stang70Fastback]

Well, I'm going to be driving the car 45 minutes to a nearby place where a member of the Car Club here has offered to swap the whole intake manifold on the car and see if that helps. Hope he knows what he's doing, lol.

[Huffer]

Why swap an IM? You could just clean it!

[Stang70Fastback]

Yeah, decided against it. They guy's kind of shady. Instead, I'm driving 8 hours up to NJ next weekend (assuming the car makes it) and I'll stop off at his place on the way up and just pick up an MAF he has lying around and swap that out at home and see if it helps...

[evolegacy]

im grabbing decke's MAF this sunday, I'll post if it improves on my end.

[STL97outback]

My car is having the exact same issue as discussed on the beginning of this thread. Mine is a 5 speed manual, 118k mile outback, stock.

In 2 weeks I am doing the full fuel filter, spark plugs, wires, air filter, pvc valve stuff, and see if that cures it.

If not, then I will do the TPS sensor. Any one know how expensive or difficult the TPS is?

Thanks

[jey]

If not, then I will do the TPS sensor. Any one know how expensive or difficult the TPS is?


Not difficult, but you will need an OBD-II scanner so the TPS can be calibrated correctly. I've got one we can use if you decide to change it out...

[STL97outback]

If not, then I will do the TPS sensor. Any one know how expensive or difficult the TPS is?


Not difficult, but you will need an OBD-II scanner so the TPS can be calibrated correctly. I've got one we can use if you decide to change it out...The TPS and PVC (these are the two I am not familiar with), do these need to be OEM or just parts store?

Can I install them with you this weekend?

I also sent you an email per your request :smt023

[legacygt420]

CHANGE YOUR PLUGS AND WIRES!!!

[STL97outback]

CHANGE YOUR PLUGS AND WIRES!!!
.....................



In 2 weeks I am doing the full fuel filter, spark plugs, wires, air filter, pvc valve stuff, and see if that cures it.

[Stang70Fastback]

Will be replacing the MAF Sensor this weekend.

Just an update on the most recent events of the past three days since I'm bored:

1. Waiting to pick someone up. Car hiccuped once (as in RPMs dropping then kicking back up) then seemed fine. Shut it off to avoid any more issues. When she got there a few minutes later, I started the car only to find the revs going all over (almost stalling then kicking up really high.) Rather than let it stall, I just decided to GO and gave her some gas. It was awful, lol. Car was hiccuping all the way up to 2500 RPM, lurching as it went, then after about 10 seconds of wild bucking the car was fine again.

2. Car was running fine then I went to give it some gas only to realize it stalled while I was coasting down the hill. I hadn't noticed because the air was on high and I was coasting in a straight line and when it stalls like that it's not violent at all, it just dies. This was right after I had been doing some doughnuts in a snowy lot so when all the dash lights came on I got really worried, but then saw the tach and realized it had died. Started it up while I was coasting at like 30 and it was fine. (Can anyone explain why the AT Temp light always flashes whenever you start the car after it stalls like that? Used to have that happen all the time when the head gasket was gone and the car would overhead and we had to turn it off while moving occasionally.)

3. Started the car after class. It had been sitting in the lot (20 degree weather) for about 90 minutes after being driven TO class (it was almost warmed up when I got there to begin with.) Started her up and the RPMs immediately started fluctuating between 800 and 1300 RPM. Watched as it got worse till it ALLLLMOST stalled, but then kicked up and jumped up to 2000, then slowly came down and kept going till it almost stalled but then kicked up to 2500 where it stayed for like 5 seconds before slowly coming down. Then it was fine.

I am AMAZED that through all of this nuttiness the CEL never comes on, lol.

[decke48]

so you did the tune up? sound like a lean fuel condition or plug exhaust to me.

[evolegacy]

a few comments in this topic is starting to make me wonder about my torque converter, i have that issue with getting little to no power for x amount of time in 1st gear. as for the RPMs dropping when it first starts to move, it only does it when the car is cold/just started up, could be normal or signs of possible issues later? idk.

other than that, i just need to do a 'good' tune-up and not this cheesy one my cousin helped me do from advance auto parts last year (2 of my plugs are fouled :-/).

[jey]

CHANGE YOUR PLUGS AND WIRES!!!

Yeah the TPS aint cheap, we'll be better off doing the plugs, wires, and air/fuel filters first since they're maintenance items.

[Stang70Fastback]

Interesting event a half hour ago:

I've noticed that one of the causes of this problem seems to be after I've driven the car somewhere, let it sit for a little while, then when I go start it again, THAT'S when it will immediately have problems. Drove the car to Wendys, spent 10-15 minutes inside picking up food, went outside. Started car, backed out of parking spot, drove forward, as I'm turning around passing the drive through lane the car want's to go straight. At first I thought it was ice jammed in the wheels (there's a lot of it, lol) but then realized it stalled. Started it again, finished the turn and it stalled again... fuck. Went to start it a THIRD time but THIS TIME nothing happened. Lights come on on the dash and that's it. NOTHING else, no ticking no noise nothing. FUCK FUCK. Tried a few more times to no avail. So I let it sit for a bit. In hindsight I MIGHT have been dumb enough to have it in drive, but I'm fairly confident it was in neutral/park for these attempts. After sitting it started... stuttered... stalled. Started it a fourth time, and it seemed to run ok. Drove it all the way home and whenever I was coasting or braking I was doing so with my left foot with the right foot revving the engine with the tranny in neutral.

Fun times. Looking forward to the 450 mile drive home this Friday for spring break, lol.

[Brockley]

want to try a new coil? i swapped mine, we could just try it out on yours...

[Stang70Fastback]

Well, let's see what happens over break. I'm going to be trying someone else's MAF, and possibly their injectors too. Also will have a mechanic I know look it over. If nothing works then maybe, but if it's not fixed, I don't even know if I'll be driving it back down :(

I've noticed though that the problem seems to be greatly exacerbated by very cold temperatures (like yesterday when it was like 15 degrees out it stalled over and over, but today when it was in the 30s it just hiccuped once or twice.)

[Stang70Fastback]

Well, swapped in my friend's MAF...

...didn't fix the issue.

[99gtlimited]

... fuel pump....??

[SubaGlue]

Im having a strange stuttering too, but its only happened once and it was when i was cruising at 70 on the highway. I was at like 3k rpm and with steady pressure on the pedal, it stuttered and hesitated. I also have to drive 450 mi home this weekend :shock:

What part of the country are you in?

[Stang70Fastback]

I go to college in Virginia (VT) but my home is back in NJ.

[SubaGlue]

I found out what my problem is (still have yet to fix it): Its the front o2 sensor. I tht the CEL was on because of the rear one, but the code said "o2 sensor 1" or something, which means it is the first one. It also explains my stuttering at any rpm and general poor running.


Obviously not the same problem. I would honestly have to say, from what Ive heard, that your tranny is on its way out. With that high mileage, its bound to go sooner or later.... And I dont think a dying trans would trigger a CEL

[Stang70Fastback]

Not the tranny, I can tell you that much. Guaranteed. Explained the problem to a Subaru mechanic yesterday and he seemed pretty sure that it was a sticky Idle Air Control Valve, which makes sense...

...don't really have the money to fix it now (the part alone is like $350 apparently) but maybe later.

[Huffer]

And I dont think a dying trans would trigger a CEL

You'd be wrong then...

[Huffer]

Not the tranny, I can tell you that much. Guaranteed. Explained the problem to a Subaru mechanic yesterday and he seemed pretty sure that it was a sticky Idle Air Control Valve, which makes sense...

...don't really have the money to fix it now (the part alone is like $350 apparently) but maybe later.

You can clean the IACV - try that.

[SubaGlue]

And I dont think a dying trans would trigger a CEL

You'd be wrong then...

My mistake- good thing its not the trans

[Stang70Fastback]

You can clean the IACV - try that.

Is that something I can do easily?

The tranny is not exactly in prestine shape, lol, but it works and I know it's not the issue.

[Huffer]

You can clean the IACV - try that.

Is that something I can do easily?

Pretty much - you just disconnect it from the harness, take it off the intake manifold, use some electrical spray cleaner or carb cleaner, let air dry completely, reinstall and see what happens. The car will have to relearn the idle, so you might as well disconnect the negative terminal on the battery too to reset the main ECU.

http://www.autotalk.com/forums/81subaru ... -1891.html (http://www.autotalk.com/forums/81subaru/where-idle-air-control-valve-99-subaru-outback-1891.html)

[LegacyRob]

Clean your throttle body and the iacv. You mentioned that it's worse cold, maybe the iacv is icing up a little as well as being dirty.

[Stang70Fastback]

I don't believe it's any of those things (throttle body, ICAV, MAF, spark plug wires, coil pack) for the following reason. Yesterday I started my car, and was letting it warm up for a minute or two (I like for the valve-tapping to disappear before I drive it.) It was idling at around 1500, as it usually does when it warms up - slowly dropping as it goes. It was just hovering at 1500, when it died. There was NO sign. It did not waver, stutter, misfire or anything. It was running one second, and silent the next. It didn't stutter and die, it just DIED. It was as if I'd turned the key. Not violent, just dead. That's not something indicative of any of these issues. It seems suspiciously like an electrical issue. People suggest there is a short somewhere. I can tell you that when it dies, EVERYTHING ELSE in the car works. So it's isolated to the engine. It might be an ECU issue, which would explain why it wouldn't throw a code.

However, the strange thing is that this "short" only happens when the engine is idling. When the engine stalls when I'm driving, which it does at least once a day usually, it happens when I get off the throttle (almost always it happens when I get off the throttle to make a turn, start turning and all of a sudden the steering gets hard and I realize it's stalled.) It's so quick and smooth that I've NEVER noticed it stalled when I was driving until I feel it in the wheel. So this intermittent "short" only happens when the car is idling... which makes me want to think it's not so much a physical short. Then again, it seems to be exacerbated by cold weather, though it has happened in warmer weather (50 degrees). So I really don't know. But i would think that a failed fuel pump, bad coil, dirty plugs, old wires, wouldn't cause this kind of instant shut down, but a sputter and die type issue (which sometimes does happen, but usually my stalling problems are 'instantaneous-deadness' issues.

[Huffer]

Ok, don't believe us, but I still believe you have an issue with the IACV and possibly a vacuum leak.

When it dies it's idling, correct? So what's operating when it's idling? The IACV, and the vacuum system.
That makes sense because even when you're turning corners you're off throttle - so the vacuum system is operating.

Clean the items we've told you clean, and see if you have vac. leaks.

[Stang70Fastback]

I don't see how the IACV being dirty weird would cause the car to instantly die when idling at a specific RPM. The mechanic I talked to told me it was likely sticking, so how would that cause the engine to go from idle to dead. When it's idling at a specific RPM, the valve is open a certain extent. It's not moving though, is it?

Regardless, I don't know how to check for vaccum leaks, and I'm still not quite sure where exactly the IACV is other than that it's at the back of the engine. Is this something that comes off easily? Could someone be more descriptive as to where it is located?

[Huffer]

For someone who is so adamant that its not a particular part, you don't know a lot about it. Maybe you should consider the idea before slamming it down.

http://forums.nasioc.com/forums/showthread.php?t=781242

You say things like "instantly die when idling at a specific RPM". It's IDLING. What is an IACV? an IDLE Air Control Valve.

[Stang70Fastback]

You say things like "instantly die when idling at a specific RPM". It's IDLING. What is an IACV? an IDLE Air Control Valve.

I'll be the first to admit I don't know much, but I am studying to be an engineer which means I like to try and understand what is going on at a physical/mechanical level. As I understand it, it's a valve that moves. The problem with it, in theory, is that it's dirty, and therefore sticking. If anything that should cause the car to get stuck at high idle, not stall... correct? How would that cause the car to go from idle to stall. It would have to close. I guess it could be a short circuit or loose connection or something. I plan on looking at it, I'm just looking for an explanation that makes sense, because the explanation that it's dirty doesn't, unless I am not understanding how it works, in which case I would like to know out of curiosity. I'm not trying to be a dick, I'm just looking for a logical explanation - that's just me being me.

Anyway, I happened to find the Subaru Service Manual on my computer (LOL) which has complete instructions for taking it off. HOWEVER, it also has directions for how to clean it, which involves just disconnecting the air bypass hose from the air intake and:

4) Slowly pour one can (16 oz) of cleaner into bypass air hole.
Cleaner:
Part No. 1050002 GM Top Engine Cleaner
Part No. X66-A AC Delco Carburetor Tune-up Conditioner

Then it talks about using their computers to check solenoid's duty ratio and adjusting the TPS to match it. Can I do this safely without having to adjust the TPS, and also are there any comparable cleaners at AutoZone that I could use instead are those two possible cleaners I should use or two different cleaners of which I should pour both down? It just says to pour that down the line and wait for the white smoke to stop.

[Huffer]

I give up. You are overanalysing and not reading anything that's been posted above.

[Stang70Fastback]

I give up. You are overanalysing and not reading anything that's been posted above.

What do you have against my trying to understand what the problem is?

For your information, I am not ignoring anything. I just bought a 16 oz can of seafoam and I'm about to pour the entire can down the air bypass hose and run it through the car in hopes of cleaning the IACV.

[Stang70Fastback]

Ok, here's what happened with the seafoam treatment:

Start car, warm up to idle, just as it gets up to temp, the idle starts wavering a bit. Before it has a chance to stall, I have my friend sit in the car and rev it up to 2k as per instructions. I unplugged the bypass hose (which caused the engine to rev strangely, but my friend kept it in check.) Started pouring seafoam treatment in and immediately the engine started to bog down and stall. I had to pour it in VERY slowly, while my friend worked the throttle like a madman trying to keep it from stalling when the RPMs plunged, but then letting off when it surged back down. Thick white smoke came out tailpipe. Car REALLY did not want to run. At one point the engine would just start dying, you could put the pedal to the floor and it would be as if it wasn't getting any gas, and then kick on again and you'd have to come off the throttle really quick. It must have stalled 10 times while we were trying to get the entire treatment into the bypass. CEL came on throwing a code of vacuum seal leak, and cylinder 1 and 2 misfires. Started the car over and over putting more and more of that stuff in. On one start a metal twang sound scared us a bit, but the car continued to run. When we finally got the whole bottle in, just keeping it running was ridiculously hard. It must have stalled another 10 times, usually very violently trying to keep going. After there was almost no smoke coming out, I turned the car off, exasperated, and worried sick that the whole engine had torn itself to shreds in the process (we'd heard all sorts of strange noises, including muffled explosions from the tailpipe.) Went inside and spent 10 minutes wondering if I'd killed my car.

Reset the ECU by unplugging the battery for a bit. Started it up, ANNNND it idled! At least it was running. Let it idle for 5 minutes which it did perfectly normally. Started driving it and to my amazement found there to be no stuttering when accelerating from a stop. Took my friend for a ride and HE mentioned the car felt silky smooth - like a new engine - and I agreed. I seemed to have solved all my problems. However, I went out for a longer 10 minute drive and there was a 1 minute period where the car wanted to stall again and idle and was revving kind of strangely, but maybe that was just leftover seafoam... Guess we'll have to wait and see, but for now it seems to have at least resolved the stuttering issue and made the car run a lot smoother - which is amazing considering how rough it was running during the treatment. I don't think a car could sound any more sick.

[Huffer]

I am hopeful that you poured the Seafoam in fairly slowly - the car shouldn't bog too badly - if it is you're pouring too fast.

Next, you reset the ECU - so now the car is relearning idle, gas/air mixes and ambient air temps. Plus your driving style.

Now that you've used Seafoam, you will want to change your spark plugs, oil + filter and fuel filter in case anything has blown past. At least do your spark plugs.

Then reset your ECU again and see how it rolls.

You may still have to take your IACV off and physically clean it from the topside.

[Stang70Fastback]

I am hopeful that you poured the Seafoam in fairly slowly - the car shouldn't bog too badly - if it is you're pouring too fast.

Next, you reset the ECU - so now the car is relearning idle, gas/air mixes and ambient air temps. Plus your driving style.

Now that you've used Seafoam, you will want to change your spark plugs, oil + filter and fuel filter in case anything has blown past. At least do your spark plugs.

Then reset your ECU again and see how it rolls.

You may still have to take your IACV off and physically clean it from the topside.

Yeah, we poured it in slowly. Took us like 20 minutes to get the entire 16 oz bottle down the tube.

Problem is not at all solved. Took the car for a bit of a further drive to see what happens. All of a sudden it started stuttering. Down the road it was just bucking, I was trying to keep it going, but I knew I was screwed so I quickly pulled into a parking lot just as it stalled. Started it something like 7 or 8 times and every time it seemed ok but as soon as I put it in gear and went to give it gas it just died. On the plus side, I GOT A CEL THIS TIME, and it was the same one that also appeared while I was doing the seafoam. I wrote it down but I can't find it now (it's still there but I haven't gotten to my car yet.) I think it said "mass or volume air flow sensor low input" which basically sounds like a MAF problem now. Long story short the car REALLY didn't want to run. I thought I was stranded, but after letting it sit for 5 minutes it started up fine. Drove home as fast as possible (I was about 13 miles away) and just as I was getting home it stalled on the road and int he parking lot twice. So back to square 1 - but this time with a CEL. Hope that's not a result of the seafoam (though the soafoam was poured in past the MAF so I don't see how it could have affected it.

Swapping my MAF with a friend's did not solve the problem a few weeks ago, so I don't know what it could be (maybe it's the harness?) I think at this point it's time to go to a mechanic and let them try to solve it.

[Stang70Fastback]

Well, I might have solved the problem. A friend of mine noticed something that I had completely missed. There is a hose that runs from the engine to the air box (underneath) on the left side of the engine (looking at it) and it was simply unplugged on the air box side and just sitting there. I have no idea whether or not that is recent or if it has been like that, but he suggested that might be the cause of all my issues. That was allowing air to leak out which meant the air the engine was getting was different than what it was reading. Since the problem is greatly exaggerated by cold temps, we were thinking this has more of an effect with denser air. The car idled for about 45 minutes with no issues whatsoever and I took it on a quick drive. Then again it was 70 degrees out and it generally runs OK. Keeping my fingers crossed!

/old-thread-bumpiness

[Huffer]

That unplugged pipe will cause a vacuum leak, which I'm pretty sure someone mentioned 2 pages earlier... well, good luck!

[Stang70Fastback]

Yeah. I know. I checked myself, but the hose runs directly behind the intake so I didn't at all see it, and it didn't make any unusual sound. And that combined with the "low voltage input MAF" CEL led me to believe something else was at fault. Drove it to class in 50 degree weather without issue. Keeping my fingers crossed. The best part is, the Seafoam treatment seems to have solved the original stuttering on acceleration issue, so hopefully everything is solved!

[Stang70Fastback]

Well, that wasn't the problem.

Back to square -23, lol.

[pdawg]

I had the same problem. It was the front o2. Bad cat with no back pressure fouled it. It did not give a cel. Had to go to the stealership to get it diagnosed. After replacement it runs like a scalded dog.

[Stang70Fastback]

I had the same problem. It was the front o2. Bad cat with no back pressure fouled it. It did not give a cel. Had to go to the stealership to get it diagnosed. After replacement it runs like a scalded dog.

I was actually thinking it might be a bad cat. I took a video at night of the car having trouble - this is how it runs most of the time now. My friend said it sounds like it's starved for fuel, so he thinks it's either the injectors or the fuel pump. The first three minutes give a good example of the issues it's having. No one was touching the throttle at any point except the one time I revved it. At 1:20 it sounds like a tractor, lol.

http://www.youtube.com/watch?v=eG3F5Yzt7YU&fmt=18

It's a good thing the belt squeals, lol, helps you hear what's going on.

[pdawg]

That is exactly what mine sounded like. Change the front o2 and see if that doesn't solve the problem.

[Stang70Fastback]

That is exactly what mine sounded like. Change the front o2 and see if that doesn't solve the problem.

Forgot to mention, lol, that the front O2 was replaced last summer by Subaru because they thought that would solve the stuttering issue.

[pdawg]

Oh well back to the drawing board.

[winston856]

How are things coming along?

My car used to sound like yours in the first vid and I had a vacuum leak from one of the hoses on my TB. I went through and replaced all the smaller vacuum hoses and the stuttering is small scale now.

I started a thread on this same issue and went through replacing a plethora of parts from the MAF to the Coil pack, plugs/wires, fuel filter, and more.

My problem still exists but it's not as bad but sometimes it'll become worse. I've got a 5MT car btw.

[BenO]

So I didn't read all 4 pages of this but, I had a similar problem that I just sort of went with thinking it was just how subarus were.

I removed my snorkus and the stuttering stopped!

Not sure if your snorkus is out yet or not.

Give it a shot and see if it works though

[winston856]

I took my snorkus off, didn't make a difference. I'm convinced I have a vacuum leak somewhere. I need someone to diagnose this. Can't I just hook it up to a computer and see what all the sensors are saying?

[VIN CODE 6]

Sounds like injectors and given the mileage I'm sure there pretty gummed up besides that certain years of Subaru's had light throttle and idle problems due to poor injector design. I would buy a set or send yours out to have them cleaned and tested. Witchhunter Performance will due it for $18 per injector. Maybe you can find someone with a spare set that you can try. Good luck!

[winston856]

Yeah injectors make sense. They're one of the only things I haven't looked at. They are originals with 227k miles on them now.

One reason I didn't do them is that I think when I looked at a set of them on SGP.com they were like $100 per injector. I'll have to check that again but that's insane!

[Huffer]

I bet Reason probably has a spare set lying around.

[winston856]

Well I got some injectors on the way, I'll post when I put them in if they make a difference or not.