See if you all can help me on this

[winston856]

Alright so I've had this problem pretty much since I've had the car, it's not a HUGE deal but I really want to get it solved and I think these things are related.

The Symptoms:

When idling especially cold (which would be fast idle), if I touch the gas lightly it's like the RPM's pause then jump. Almost like the car coughs. It doesn't backfire but it's similar to a pop. It's going perrrrrrrr pop perrrrrrr, that pop is when I touch the gas. It's not a POP but a little tiny stutter kind of pop.


The Symptoms, Continued:

The next bit is when I'm warm more so than cold. If I rev out first or second gear. Lets say first, if I'm in first and going 10-15MPH the RPM's are over 2k, like 2500 ish.

Holding the throttle steady the car lurches or jerks a bit. Think of it like when you turn on your garden hose if it hasn't been used in a long time the water comes out in a stream but there are breaks where it sputters for a second.

It's noticeable when I hold the throttle steady like I was saying, the car will lurch or jerk not real hard but you can feel it.

It seems that these two things are related or so I think.

Things I've changed on the car:

New Plugs (NGK copper)
New Wires (NGK Blue)
New Coil pack (MSD Blaster)
New Knock Sensor (OEM)
New PCV Valve
New Air Filters
New Front and Rear O2 sensors (OEM)
New Fuel Filter (OEM)

What could this be, I was thinking Throttle position sensor since it's sort of throttle related but I don't know what could cause this. Anybody experience this or something similar? Have any thoughts?

[Huffer]

I don't see a fuel filter mentioned in the tune-up list... that might help.

[Perdue]

Change the Fuel filter as Roger stated. It's not likely your source imo, but it probably needs it and wouldn't hurt.

Try cleaning your MAF Sensor and TPS sensors. I used rubbing alcohol and a q-tip to gently clean the MAF sensor on my BD. Be really careful, as you don't want to damage it. The specific part you're looking to clean is the little wire suspended inside the sensor housing. I'm pretty sure you use carb cleaner to clean the TPS, but I'm not sure. If you can't clean it and get it working, then replace it.

[d1giPhux]

I wouldnt use a q-tip on the MAF sensor.. just get MAF sensor cleaner and spray it down real good. Sounds like it could be the MAF.. i'm having a same sorta issue on my car as well.. sounds pretty much just like yours.. except for the lurching when you shift.. mine just seems to have lost some torque / power in the low rpm range.. hmm.

When idling and you stomp on the gas just to rev it up.. is there a pause right when you step on it? Thats what mine is doing... also.. yours lose any torque? Mine kinda hesitates to accelerate well between 2k-2.5k rpms... sometimes up even till 3k. Hopefully we can help each other out on this one.. ive replaced all of the same things you have.. minus the knock sensor... this started to happen to me after i got 2 new cats / o2 sensors installed... almost feels like i still have a small exhaust leak.

[jey]

If you think it's a problem with the TPS you can get a good OBD-II reader on it and monitor the throttle position reading.

[liquidracing]

nope

[winston856]

Sorry guys I new i forgot something, I replaced the fuel filter about 5k miles ago.

[winston856]

I wouldnt use a q-tip on the MAF sensor.. just get MAF sensor cleaner and spray it down real good. Sounds like it could be the MAF.. i'm having a same sorta issue on my car as well.. sounds pretty much just like yours.. except for the lurching when you shift.. mine just seems to have lost some torque / power in the low rpm range.. hmm.

When idling and you stomp on the gas just to rev it up.. is there a pause right when you step on it? Thats what mine is doing... also.. yours lose any torque? Mine kinda hesitates to accelerate well between 2k-2.5k rpms... sometimes up even till 3k. Hopefully we can help each other out on this one.. ive replaced all of the same things you have.. minus the knock sensor... this started to happen to me after i got 2 new cats / o2 sensors installed... almost feels like i still have a small exhaust leak.

Yes and no. :smile:

If my revs are at idle and my engine's warm, if I tap the gas sometimes it will do that little cough thing and rev up, it's like a split second stutter. If my revs are at 1000rpm+ it doesn't do this.

I still have power down low, more now since I put my blaster coil on but that's aftermarket.

I can step on it at any time and it will rev no problems, it's just if I hold the throttle steady in 1st (or 2nd) and am trying to merge with traffic in town I can feel it jerking a little. When it's cold if they're under 1500rpm's and I tap the gas it will do that little cough thing.

[liquidracing]

nope

[d1giPhux]

Yeah.. that definitely sounds like something fuel related.. maybe injectors like stated above.. hmm.

Also.. where did you get that coil? Is that a neon coil?

Weird.. I'm still trying to figure out my problem as well and having no luck. :/

[jmgtp]

Holding the throttle steady the car lurches or jerks a bit. Think of it like when you turn on your garden hose if it hasn't been used in a long time the water comes out in a stream but there are breaks where it sputters for a second.

Am I reading this correctly? In that when you shift from 1st to 2nd gear you are holding the throttle steady and the car jerks when you engage 2nd?

If so, solution: let go of the throttle!

By holding the throttle you arent allowing the engine to fall in rpm and essentially not allowing things to 'rev match.' The whole point of shifting is to maintain or increase vehicle speed at a lower engine speed. You're essentially low speed power shifting it and if the car was fwd you'd probably be barking the tires when you shift.

If thats not what you meant then my bad!

It's normal for an engine to have that slight hesitation/dip down when its stone cold. But sounds like you have a more serious issue if there are pops and such. Sounds like a fueling or spark timing issue. I'd check for weak spark and/or faulty spark plug wires first.

[liquidracing]

nope

[winston856]

liquidracing had it right. I'm not powershifting, I know how to properly drive a manual, but thanks for checking me on that :smile:

I'm going to change out my ECU tomorrow so we'll see what that does.

Also I have to mention, the condition gets worse when it's warm out. It was cold out tonight (39ºF) and the car was loving it, pulled harder etc...

If the car is hot it'll do that jerking if I hold the throttle steady in 1st above 2000 RPM. If I'm just driving normally I don't notice it very much at all, but if I exaggerate my shifts, letting the engine rev out longer I can feel it.

This is only with light throttle, less then 1/2. If I give it more gas or just floor it I take off.

[Huffer]

Could be clutch related too. Might need adjustment if it's not grabbing correctly.

[liquidracing]

nope

[winston856]

I'm going to change out my ECU tomorrow so we'll see what that does.

Also I have to mention, the condition gets worse when it's warm out. It was cold out tonight (39ºF) and the car was loving it, pulled harder etc...

If the car is hot it'll do that jerking if I hold the throttle steady in 1st above 2000 RPM.

If I give it more gas or just floor it I take off.

detailing the coldness i'd say at that temp you're running richer(the way it should be) but, when warm it sounds like you're leaning out kinda weird-ly, maybe not a huge amount but enough for lean mis-fires to occur. now i'm feeling that ecu is more the suspect, but, still lookin' at the canister.

maaaayyyybeeee..........bunk maf.

hmmmm.......ecu, canister, injectors, then maf. that's the order i would check in. good luck, let us know how it goes.

How do I clean the MAF? I know there's a way.

Also, is that canister located more on the passenger side? I swear I've seen a black canister while under the hood before.

[d1giPhux]

Its part of the intake system (on the passengers side of the car connected to the air box).. and looks like this :


http://www.4turbo.pl/katalog/images/22680AA160.jpg

in this picture it can be seen to the left of number 4:

https://sl-i.net/FORUM/images/imported/2008/11/IMG_3889-1.jpg

here it is again.. its the square box looking thing with the plug going into it on the tubing (has the giant STOP sticker on it):

https://sl-i.net/FORUM/



You just unscrew it.. then spray off the sensor inside the tube using MAF sensor cleaner (which you can get at autozone, or advance auto.. etc. )

[SUBBIEEDUDE!]

i used to have this same exact problem. i actually stalled out on the highway though a couple of times. accelerating would run fine, but when you would stay at like 3k rpms it would sputter and like jerk. i ended up change my mass air flow sensor and i havent had the problem since. so i would try going to your local junk yard and snagging one of those for like 10-15 $. other then that. i dont know what to tell you. it could be alot of things.

[winston856]

i used to have this same exact problem. i actually stalled out on the highway though a couple of times. accelerating would run fine, but when you would stay at like 3k rpms it would sputter and like jerk. i ended up change my mass air flow sensor and i havent had the problem since. so i would try going to your local junk yard and snagging one of those for like 10-15 $. other then that. i dont know what to tell you. it could be alot of things.

I think I'm going to try and clean it first, but I'll look into getting another.

Would the MAF from a 2.2L work?

[HeresMyMind]

any 2nd gen leggy will work, or 2.5 rs w/ maf.

-B

[Okin DaVanh]

also, don't forget to make sure all the hoses to the intake are fully connected. I had a similar scenario happen to our car, and it was 1 of the hoses that wasn't connected.

[jmgtp]

liquidracing had it right. I'm not powershifting, I know how to properly drive a manual, but thanks for checking me on that :smile:


Haha, okay! Sorry if I came off harsh then, its just how I read it.

My other car does something similar when the clutch is cold it doesn't like to slip in the slightest and operates like a switch: its either 'on' or 'off' with no inbetween. A few minutes of driving to get some heat into it and it is normal.

[winston856]

Well I switched ECU's and that didn't make it go away, I switched MAF's today with a spare I had here, so we'll see how that goes tonight.

[peugoby]

What octane are you running in your '96?

'96 2.5 GT's ask for Premium. Run some fuel system cleaner through if you've been running reg. and then fill up with a few tanks of premium to see if it goes away.

[Huffer]

Actually you can run the 96GT engine with a later ECU and run 87 octane without any problems.

[peugoby]

True, Winston did say he switched ECU's but didn't say the ECU was out of a latter GT.

Just quoting cars101: "premium fuel recommended"

I guess if I were in his shoes I'd make sure I was starting with the recommended octane.

[Zedhead]

TPS

Get a meter and check for a good signal ALL the way thru the throttle sweep.

I'd almost bet You have a dead spot somewhere near 1/4 throttle.

[winston856]

TPS

Get a meter and check for a good signal ALL the way thru the throttle sweep.

I'd almost bet You have a dead spot somewhere near 1/4 throttle.

Changed the MAF and it didn't do much, the problem is still there.

I measured my TPS today, I thought it was it at the start and it looks like it might be my problem.

The book states the voltage with the throttle closed must be between 0.5-1.0v, and it measured 0.2v and was jumping around.

The volts must also be between 4.5-5.0v with the throttle fully open (WOT), they measured about 3.5v and were jumping around a lot, bouncing from 1-3v.

So suffice it to say, I think my TPS is on it's way out. I've got a new one ordered and will put it on tomorrow.

And yes I've been running 92 octane since I bought the car because read that the '96 2.5L's recommended it. Since I have the '97 2.5L ECU theoretically I could run 87, but I'm not doing that until I get this problem sorted out.

[Zedhead]

With the readings You posted, I concur. The TPS is shot.

[winston856]

Well I changed it and if I had to say something right now perhaps the problem has gotten a little better, but nothing earth shattering.

I'm going to be driving tonight at work so I'll have a chance to see if anything further happens.

I changed the TPS out for the new one today and aligned it properly, works fine no CELs. I then reset the ECU and took her out for a spin.

After driving for a while to get it warmed up (read: 10 miles), I proceeded to stop and do a few light throttle applications. Like backing out of a parking spot, slowly inching forward in a drive through etc.

The stumble is still there so my next objective is to get a video of this thing so you all can hopefully see what I'm dealing with here.

I still do need to check that carbon can but I ran out of time for today and won't be back under the hood until probably friday, maybe wednesday.

I probed the TPS before and after I checked it. I have the 3 pin TPS, pin 1 is Ground, pin 2 is REF and pin 3 is SIGNAL. The book tells me to backprobe pins 1 and 3 and read the voltage.

I did this with the old and new TPS sensor and still was getting jumping readings with both, I don't know what this means. Maybe I was probing it wrong. I used little paperclips to stick in the back since they were so small, then touched the probes to them to get the readings making sure I touched the negative probe to the ground and the positive probe to the SIGNAL.

So, I don't know, I'm frusterated and a little disappointed.

[winston856]

I think I'm going to check out the Idle Air Control Valve next, that is known to be a problem on certain Subaru's.

Mine's located to the left of the throttle body, not on top of it which I think is how the newer phase II engine's are.

I'm trying to check things that are related to the throttle and or idle since that's where the problem is. :smt021

So I've checked the MAF and TPS which didn't solve it. I still have the Carbon Canister and the Injectors. I did a little reading on the IACV and my idle does hang so I'm still going to be checking that out, but I don't think it's the problem, though it could be.

It does it more when warm, and is exaggerated with a load on the motor i.e.

I'm sitting in a parking space. The engine's idling, I can touch the gas a little bit and it will just start sputtering and running really rough. Sometimes it's for a few seconds then the idle picks up (foot still on the gas this whole time), and sometimes I can get it to stumble longer. When this process happens I can make it worse if I start letting out the clutch at the same time it starts bogging/stumbling. Sometimes it will die if I do that.

I need to get a video of this.

[liquidracing]

nope

[liquidracing]

nope

[winston856]

Well I changed it and if I had to say something right now perhaps the problem has gotten a little better, but nothing earth shattering........So, I don't know, I'm frusterated and a little disappointed.


will you please, for the love of god, purge you egr overflow canister FIRST! :smt013 it costs nothing. :smt007 it is the black cylindrical canister behind left hand headlight. please, try it. it worked on mine. i have a '96 LSi, which btw, is YOUR car, right down to the ecu. the only REAL difference is i have leather standard and a moon/sunroof. PURGE the canister. there is a draincock on the bottom of it.

Yes yes I will do that next. How do I purge it? Just pull it out, open it up and blast it with the hose? :smt068

[winston856]

So I checked it out today while I was changing my radiator. I'm not sure how exactly how to purge it.

There are two hoses connected to the top of it and a hose going out the bottom over the frame rail and down underneath the car somewhere. So far I haven't seen a draincock.

[Zedhead]

When You changed the TPS, did You calibrate it?

.5V throttle plate closed, 5V throttle plate fully open?

After thinking about this, Your problem sounds like it could be the EGR valve not closing properly.

If the EGR is open (even partially) while at Idle, it's just like adding unmetered air to the intake. Causing a vacuum leak type symptom.

[winston856]

When You changed the TPS, did You calibrate it?

.5V throttle plate closed, 5V throttle plate fully open?

After thinking about this, Your problem sounds like it could be the EGR valve not closing properly.

If the EGR is open (even partially) while at Idle, it's just like adding unmetered air to the intake. Causing a vacuum leak type symptom.

It could be the EGR I suppose. My problem is random though, sometimes there is no hesitation for a while, other time's it's bad.

I learned something else the other day while changing my radiator, to bleed the air out I had to hold the RPM's between 2-3k for 5 minutes. While holding them at 2700RPM, the RPM's would fluctuate + or - 200 RPM. So when I had the engine RPM at 2700, it would slowly dip down to 2500, then back up to 2700, then up to 2900, then back down at so forth.

So this problem I'm dealing with, this hesitation off idle, is really over the entire RPM range. If my RPM's fluctuate like that when I'm holding the throttle steady, I believe when I have it in gear that fluctuation is what makes the car "surge/buck".

I didn't calibrate the TPS by voltage because I could get good readings. So I had it loose with the car idling and adjusted it until it idled smooth and there were no CELs.

Suffice it to say I don't believe my old TPS was flawed.

I'm looking at:

The "carbon canister" (there's no procedure in the Haynes manual to check it. I can't find the petcock either, unless it's what the hose going out of the bottom leading under the car is :?: )
The EGR Valve
The Injectors

[Zedhead]

Try holding the throttle open to 2500 RPM and watch the EGR. Se if it's operation is inducing the RPM fluctuation?

[winston856]

So I played with the egr today. I did the first test in the book which consisted of me revving the warm engine to see if the egr moved which it did. Next I have to get out the hand pump to see if it'll hold 10" of vacuum.

[Zedhead]

Well I changed it and if I had to say something right now perhaps the problem has gotten a little better, but nothing earth shattering........So, I don't know, I'm frusterated and a little disappointed.


will you please, for the love of god, purge you egr overflow canister FIRST! :smt013 it costs nothing. :smt007 it is the black cylindrical canister behind left hand headlight. please, try it. it worked on mine. i have a '96 LSi, which btw, is YOUR car, right down to the ecu. the only REAL difference is i have leather standard and a moon/sunroof. PURGE the canister. there is a draincock on the bottom of it.


Could You post up the procedure for purging the canister?

[winston856]

Alright here's an update.

I went through and replaced about 8 feet of vacuum hose in my engine bay, most if it running from the EGR to the BPT and TB along with some of the EVAP system.

The WAS a vacuum leak on a hose that had got severed when I was replacing my battery cables. There was enough hose so I just attached it and that was that. Well it decided to get about an inch long split on the underside so you couldn't see it without pulling it off.

Coincidentally the car has no vacuum from that hose at idle but as soon as you crack the throttle plate it drew vacuum, so there was a leak.

The result? Well the idle speed was higher after the leak was fixed. This caused me to re-adjust the TPS and now it idles within spec (600-800 RPM, it's about 700).

What I'm dealing with now is hanging RPM, I'll start the car up and the RPM's will shoot up to 1700 and SLOWLY work there way down to idle but it takes about 25-30 seconds. Even if I take off and drive, if I come to a stop they'll hang around 1300 for about 30 seconds and come down to idle.

I STILL have a SMALL hesitation sometime like before but it's GREATLY reduced, it's almost not there. I know when the throttle plate's closed the IACV takes care of the idle speed, I have a phase I engine so I can't use the "how to clean your IACV" how to posted on NASIOC. It's located on the passenger side of the TB and has a vacuum hose and a coolant hose connected to it.

So, unless you all have some other suggestions about hanging idle speed....

[Huffer]

The idle speed is actually fairly normal, if the IACV hasn't been cleaned OR the grounds are a bit suspect OR the ambient temps are below 50F. It should disappear once the car has warmed up properly.

I have that issue on my car.

Good to know you got the rest of it sorted!

[winston856]

The idle speed is actually fairly normal, if the IACV hasn't been cleaned OR the grounds are a bit suspect OR the ambient temps are below 50F. It should disappear once the car has warmed up properly.

I have that issue on my car.

Good to know you got the rest of it sorted!

Yeah, I think it's somewhat normal. The IACV test if fairly simple, just warm the car up to normal temps shut it off and pull the IACV, it should be fully closed or open or something like that.

That's next, probably wednesday.

[winston856]

Just drove to school and the hesitation is still there but like I said is about half what it was with that vacuum leak.

[winston856]

So I took care of my hanging/fast idle. My cruise control cable was adjusted too tight holding the TB open partially.

So now I'm back to square one, it still hesitates sometimes.

I was playing with it this evening and discovered that if I held the throttle slightly at about 1000 rpm then removed my foot suddenly, the idle would drop to about 500 rpm and the engine would shudder a bit, then it went back up to about 600 where it's at.

I still need to pull the IACV and look at it as well as take voltage measurements. From what I understand (on the phase 1 engines) the motor is electromagnetic so it can't wear out. It can however become gummed up with crap from the PCV line and that wouldn't allow it to close/open all the way so that might need a cleaning.

If I keep the RPM steady at say 1500 or less the engine will surge a bit so I think I'm dealing with some sort of vacuum leak. I feel like I'm on a wild goose chase :smt021 :-?

Thank you all for being patient with me and helping me thus far, I really appreciate it. :smt006

[winston856]

Tried what was in (http://www.sl-i.net/FORUM/viewtopic.php?f=11&t=9085&hilit=IACV) that thread and it didn't do shiiiiiit.

Well, another thing it's NOT...

[winston856]

Hey guys I have a thought. Since I think I'm dealing with some sort of vacuum leak here, I wondered if I could do the old school vacuum leak test of spraying the base of the TB and intake manifold with carb/brake cleaner to see if the idle suddenly picks up which would indicate a leak.

Is that a plausible idea?

I'm going to tear the IACV out and clean it over my winter break which begins next week, just trying to eliminate other possibilities.

Edit -- I'm also going to check the timing.

[winston856]

Hey guys I have a thought. Since I think I'm dealing with some sort of vacuum leak here, I wondered if I could do the old school vacuum leak test of spraying the base of the TB and intake manifold with carb/brake cleaner to see if the idle suddenly picks up which would indicate a leak.

Is that a plausible idea?

I'm going to tear the IACV out and clean it over my winter break which begins next week, just trying to eliminate other possibilities.

Edit -- I'm also going to check the timing.

Nobody's done the carb cleaner trick?

[Huffer]

Sorry, missed the post. Yes you can try the carb cleaner trick.

[Zedhead]

Another thing to try, should be done every 40Kmiles anyways, is to clean the EGR system. If the pintel doesn't seat completely, it'll allow unmetered exhaust gases to be continually dumped into the intake. Just like a vacuum leak.

[winston856]

Another thing to try, should be done every 40Kmiles anyways, is to clean the EGR system. If the pintel doesn't seat completely, it'll allow unmetered exhaust gases to be continually dumped into the intake. Just like a vacuum leak.

Yeah I was reading about that in the book, cleaning the EGR valve's "poppet". I'll see how much the IACV is gunked up but I know my engine has a fair amount of blowby so it could be pretty gooey. I aim to install my oil catch cans over the break as well, or at least one on the PCV line.

[winston856]

Update, I changed out the IACV for another used one in better condition from another car. It was slightly different but the gasket on the bottom of mine was half gone, literally flaking off. Here are some pics of the two, the shitty one is the one that came off my car. So how bad was it?

I noticed a difference, the car is smoother now and I don't have to push as much on the gas pedal to make it move, initial acceleration is improved as well. So I think I got part of the problem here. I reset the ECM after I changed this by just disconnecting the positive battery cable but I didn't step on the brake so maybe I should go reset it again.

It still will hesitate if I'm in neutral and touch the gas the RPM's go up to about 1000 and the engine runs all rough sounds like someone with phlegm in there lungs trying to hawk a loogie. So I don't know what else to check.

Sorry for the shit pictures.

https://sl-i.net/FORUM/images/imported/2009/04/IMG_0171-1.jpg

https://sl-i.net/FORUM/images/imported/2009/04/IMG_0171-1.jpg

https://sl-i.net/FORUM/images/imported/2009/04/IMG_0171-1.jpg

https://sl-i.net/FORUM/images/imported/2009/04/IMG_0167-1.jpg

https://sl-i.net/FORUM/images/imported/2009/04/IMG_0165-1.jpg

https://sl-i.net/FORUM/images/imported/2009/04/IMG_0164-1.jpg

https://sl-i.net/FORUM/images/imported/2009/04/IMG_0163-1.jpg

https://sl-i.net/FORUM/images/imported/2009/04/IMG_0172-1.jpg

https://sl-i.net/FORUM/images/imported/2009/04/IMG_0173-1.jpg

[winston856]

So how does it look?

[Huffer]

Looks a lot better - if you are still getting that hesitation & sticking high idle, look at your electrical grounds (and consider installing a ground kit). You might also consider the MSD mod.

[99gtlimited]

you gotta disconnect the negative battery connection to reset the ECU, you should always disconnect this one first and reconnect it last to be safe.

glad to see you fixed this finally. this thread almost died without a cause.

[Okin DaVanh]

I swapped out my IACV looking to repair what was actually a bad Knock Sensor. After replacing it I swapped back to the original and changed the sensor instead. I haven't had an issue since.


Not saying this is your problem, just to ask how did you adjust it to get the propper settings?

After I replaced everything, I had to hook it up to our scanner while adjusting just about every part I touched in the 1st place. That sucked, but E.S. has been running good ever since (Knock on wood)

[winston856]

Alright well I suppose I'll do a recap of everything I've done so far, all new.

NGK copper Plugs
NGK Blue Wires
MSD coil pack
Air filter
Fuel Filter
IACV (used, new to the car)
TPS
PCV Valve
Paranoid Fab. Grounding Kit
New battery cables
All new vacuum lines
Knock Sensor
MAF (used, new to the car)

I'll add more if I remember something.

The main issue now is mainly when it's idling and I step on the gas the rpm's sputter for a split second then jump up. I need to take a video of this to make it clear, it's hard to explain. Changing out the IACV has made an improvement, I can feel it in the acceleration and the exhaust doesn't smell so pig rich now. There is still something else not right with her though.

[legacygt111]

Are you still having the "hesitation" issue ? my car does the same thing, it feels sort of bumpy (back and forth) in 1st or 2nd (low rpms). Also when i shift from 1st>2nd i get like a big "tchhh" kind of sound (release of air), almost like a really bad b.o.v (even thoe i have a N/a 2.5). And this sound is less loud from 2nd>3rd and non-existent when gearing up to 4th or 5th. Any ideas ??

[Huffer]

winston - I know this is going to sound ridiculous, but I just noticed that you have a 96GT. This vehicle/ECU requires that you run premium fuel.

However, some people on NASIOC have discovered that if you run a later model ECU (like a 1998 GT) then you can run regular fuel and gain power.

Depending on the cost for a used ECU (I sold one WITH an engine for $250) you may want to consider this as well. It's an easy change out, disconnect the batter for a few mins, hit the brake pedal, remove ECU cover/carpet, 3 bolts, 3 plugs, reinstall.

[winston856]

winston - I know this is going to sound ridiculous, but I just noticed that you have a 96GT. This vehicle/ECU requires that you run premium fuel.

However, some people on NASIOC have discovered that if you run a later model ECU (like a 1998 GT) then you can run regular fuel and gain power.

Depending on the cost for a used ECU (I sold one WITH an engine for $250) you may want to consider this as well. It's an easy change out, disconnect the batter for a few mins, hit the brake pedal, remove ECU cover/carpet, 3 bolts, 3 plugs, reinstall.

It doesn't sound ridiculous, I've already got a '97 GT ECU in there :smile:

I am still having the hesitation though I have done a few more things. I've changed the injectors and that helped out and I also seafoamed the shit out of the motor and now it's running pretty nice. Every now and then it will still hesitate though..

Huffer, I think you have the same problem as me. I was watching your video in the sound clips thread with your GT and when it was idling and you step on the gas the rpm's "dip" for a split second then climb.
http://smg.photobucket.com/albums/v643/Huffer13/Icebox/?action=view&current=090801_STiAxleback.flv

That video after halfway through when you touch the gas the rpm's "dip" then sort of go "oh shit guys we're going the wrong way" and climb up quickly to where they're supposed to be and then it's fine. It's just RIGHT on the initial throttle tip in, after you're on the throttle like 5% the rest of the way is perfect.

Get what I'm saying?

[eekay]

My car also does the "RPM dip" at very first throttle touch. Always has since it was brand new. Not sure if it has to do with the air system or not, but that's kind of what I'm expecting. It doesn't really bother me though. It does seem that the engine is unresponsive for that split second but if you anticipate the dip you can drive it just like a normal car. Otherwise, no stuttering of any kind over here.

[Huffer]

Yep - I get what you're saying. I honestly never thought it was a problem per se, just a foible of owning a Subbie.
My last two Subs did that same thing too, and I never had an issue with it, regardless of the driving.

I am glad to know that my video was clear enough to make that out though! :D

[winston856]

I can't believe that's normal, idle should be smooth on and off the gas pedal.

But seeing your newer car doing it makes me wonder now if it's more common than I thought and perhaps just a quirk of the design.

It still pisses me off though, how hard is it to just have a smooth idle transition? FUCK!

Anywho I've still got a bit of wiring to take care of from my 5MT swap, it still thinks there's an auto in there when the clutch is up and there's a CEL. P1722 auto trans high input signal.

That should get taken care of tomorrow and it might have an effect on things. I still have a few sensors to change like the coolant temp and I'm thinking of changing the fuel pump as well because after changing the injectors the car has noticeably more power. The fuel pump is original as far as I know with 231k on it as of now.

I know it's not supposed to have that dip though because say if I'm decelerating and I touch the gas it backfires, just one single pop. That tells me there's a lean or rich condition for the second and it's not right. :smt021

Maybe I'm just getting to obsessive here but the car should run smooth dammit! :shock: :-?

Oh and yeah your vid was clear, sounds pretty good btw.

[Huffer]

Subaru's run rich from factory. My 2000 L Impreza w/ EJ20 SOHC had pops and rumbles with just a 2.25" catback exhaust.

It ain't no thing - you could try the MSD mod and the STi fuel pump to see if that helps, maybe a PP6 piggyback ECU if you're really serious about leaning out the ECU maps.

[winston856]

Got the MSD coil on there already :smile: Did you even read my mod list? :razz:

Got a few lines on and '06 and '07 STi fuel pumps, I'll probably end up getting whichever one comes with the harness.

[Huffer]

:lol:

sorry!

[97Scoobyl]

I know in cases that auto trans fuel trims will be different than manual fuel trims

[eekay]

maybe a PP6 piggyback ECU if you're really serious about leaning out the ECU maps.

I'll be doing this some time soon myself along with a (hopefully) good speed density setup. My car runs extremely rich due to the MAF and a non-recirc BPV setup. However, I'm not sure if the PP6 is still available? Last I saw they were phasing them out and pushing the PP8. Might still be some 6's left though. Pretty decent piggies for the price.

[Huffer]

Make sure if you're tuning the car you're using a wideband O2 sensor. Otherwise you'll be guessing. :)

[eekay]

Yup. Been doing quite a bit of reading lately about tuning for the speed density. Apparently, which will be time consuming, you can use two multi-meters to get the differences between ECU and MAF readings and go from there. Not sure how I want to do it yet. May end up having a couple of tuners I know do it instead while I get my alignment and turbo tune done.

[winston856]

So I'm about to buy an '07 STi pump for $35, the guy doesn't have the harness, says it will plug and play with any subie, Do I need the harness? I thought you needed the pigtail thing for the walbro pump.

[Huffer]

You'll need the harness. Very few 07 STi owners know much about the older subs.

[winston856]

Any idea where to find one, this guy doesn't have it. Can I buy it from SGP or something?

[Huffer]

I guess so - you'd probably have to find the P/N though.
Personally I'd just wait to find someone who's totaled their car and is parting out.

[winston856]

Yeah I'm pm'ing a few more guys. Somebody's gotta have the harness too.

[iampetro]

so i just went through the thread and i think im getting the same 1st and 2nd gear jerk/ hesitation when keeping a constant speed... did anyone find out how to fix our problem???

i couldn't quite find the exact solution in the thread.

i have 2 month old new NGK plugs and wires