acceleration issues, please help!!

[ivanwakeup]

ok guys, so recently i've run into an issue with my 99OB limited. a few days ago, the car started jerking all over the place under acceleration. was driving completely fine, then all the sudden this started happening. i've tried a few things so far to remedy the issue (namely spark plug change, just seafoam'd it as well) but it still comes back. here are a few patterns i've noticed.

the car runs absolutely fine when cold. after about 15 minutes of running is when the problems surface. I've noticed it generally starts happening when under heavy load, but then once it happens it just gets worse and worse until i shut the car off.

a few of the times its happened i get a flashing CEL (random misfire, i take it). which would lead me to believe something in the ignition system. however, the problem seemed to surface rather suddenly and i'm pretty sure my dizzy and wires are quite new (just changed the plugs today).

the issue kind of feels like everything is going fine, but at certain RPMs the car will jerk, and the more throttle you give it the more power it seems to lose. almost like it feels choked. the rev sounds quite weak as well, not as brilliant as it usually does.

so what are you guys thinking? i couldn't really pinpoint a problem but i'd like to. i have a new fuel filter which i'm throwing in, and i'll make sure i have no vac leaks tomorrow.


i want to jump on ignition problem, but if this is the case, why does it only happen when warm? is it my IACV possibly?


its probably worth it to add that i recently mocked up my own short ram intake, and i remember reading a while back that the filter i used was notorious for using to much oil on the filter element, and could sometimes clog or block the MAF. again, if this is the case why would my problems only take place when the car is warm? just sort of thinking out loud here.


any help appreciated!!!!!

[Dead91silvia]

Ok, this could be a number of things...

-bad coil pack
-bad plugs
-bad wires
-weak fuel pump
-low fuel pressure (plugged lines/filter)

If you just used Seafoam, change your filter to start since you have one already. Doing plugs and wires is kinda easy, but if the wires are now, dont bother.

It could be a fuel pump, but most of the time when they go bad, they just die and dont work at all. Coil packs are also know to go bad.

It sounds to me to be spark related more then anything. So if your plugs and wires are old, change them. It could also be the oil pack though too. I have a slight misfire on my 98 and it's all in my wires that I have been too lazy to buy and I know this from all the corrosion at the coil pack.

[lord flashheart]

If its a 22 then I bet its the sparkplug tube seals leaking.
It's a comon issue. When they leak oil into the spark plug holes the spark plug wire sits in oil. After so long of sitting there the oil starts to carbonize. Carbon is a conductor of electricity, where as gas is a insolator, so under high load there is more fuel molicules between the dieode, so the spark is following the path of least resistance, which is thru the carbon instead of thru the fuel. This causes a misfire.

It also could be fuel side. Low fuel pressure makes it run lean, which can cause a misfire just from fuel ratio.

Do you know if its related to open loop/closed loop?

So are you assuming the code is a misfire or is that what code you got when you pulled it?

[lord flashheart]

The reason I ask if its related to open loop or closed loop is because that would likely be related to the mass air flow sensor.

[ivanwakeup]

its the 2.5, not a 22- so does that rule that out?

anyway, i cant say for sure how old the wires/plugs/coil pack is. when i pulled the plugs they all looked completely normal, the diode had normal wear and tear (if much at all) and the color was a nice golden brown as i assume you'd expect. i am pretty sure that the coil pack is not OEM, as it bolts into only 3 out of the 4 holes.


MAF is sounding more and more likely, apparently that is quite related to whether the car is heated up or not, but i still can't be sure.

[Huffer]

Does it only do it when it's warmed up?

Or can you romp on it when the engine is cold.

[lord flashheart]

That's what open loop closed loop is. Usually your car is in open loop until it warms up, then it goes closed loop. Ironically the mass air sensor is used more in open loop, so its kinda unlikely... I would find out what the code is.. thats probably a big part of the puzzle.

[Huffer]

I'm betting it's the knock sensor

[ivanwakeup]

well, i actually bet if i romped on it hard when cold i'd get the issues, maybe just not to the same degree as when its warm. last time it happened it didnt happen until i loaded up the motor hard (going up a hill) even though the car had been warmed up for 10 minutes or so already. the problem is, once it does happen even normal driving gets worse and worse until i shut the car off.

on the subject of getting the code, is there an easy way to get it myself? i dont have a code scanner, is there a service connector i can jump and count the flashes on the CEL? (was able to do that on a few past cars). the CEL is and on and off kind of thing, usually when i replace something or start the car up on a new day the CEL is gone, not until later after driving it more does it come back.

[Huffer]

If you're located near an autoparts store, just roll in there and ask them to scan the car. It's a 99, so OBDII compliant. That's the easiest way. Or find a friend that has one that'll let you borrow it for a couple of days.

Clear the codes, drive it and see which codes reappear. Usually the first code that pops up is the main culprit.

PS. Update your profile with your location, and put your vehicle in your signature line.

[ivanwakeup]

the knock sensor is under the manifold, little circular black looking thing right? anything special for replacing that?

and will do on the code reading. although if my code is for a misfire, that doesn't really narrow it down to anything save ignition problems right? i'll report back at the end of today and see where i stand.

[Huffer]

knock sensor looks like a little donut with 12mm bolt through it. It's under the intake manifold slightly - on your car you may need to loosen the plastic intake chamber (if you are stock) and reach your hand under the manifold to get to it. I used a long extension and short socket to loosen the bolt then by hand to finish it.

If your code is for a misfire, that usually does mean a bad set of plugs, wires, or ignition coilpack - however an incorrect reading by the knock sensor can cause your car to lug and stumble. My car did exactly that when my knock sensor got wet - I got a knock sensor code first, then a misfire code.

ALWAYS pull the codes when your CEL comes on. Otherwise you're just guessing at things - that's the whole point of the OBD system, to help diagnosis.

[ivanwakeup]

alright, so a little more prognosis:

the car literally drives fine until its been driven for about 10-15 minutes. can rev fine, feels like full power, good idle. only later does it start to lug, and this happens slowly. the idle seems like it gets lower and lower, power drops off, and it starts jerking all over the place under acceleration.

flashing CELs when this happens are a common occurence as well.


i should also note the exhaust smells pretty lean, or at least i think. it definitely doesn't smell sweet like it does when its rich. anyway, i'm going to take a trip to the junkyard and snag a neon coil pack and some new wires too. i can't really drive the car to the pep boys (dont know if it will make it that far) so i'm just going to replace this stuff and see where i'm at.


is it possible that catalytic converter issues could cause this? this is something thats been in the back of my head since it started happening. it seems like if they were clogged they would have issues regardless of if the car is warmed up or not though.

[Huffer]

You need to pull the codes. Snagging parts is pointless without a proper diagnosis. Go buy a code reader; you'll use it more than once and it will save you money.

If the car is warmed up, and starts to lug, idle funny and generally run like a dog, my bet is that you have a cracked vacuum hose that connects to the intake - when engine parts like rubber heat up, they expand and cracks can form that appear and create fluctuating values for the ECU to measure. So, I'd see if there's a cracked hose between your MAF sensor and the throttle control.

[lord flashheart]

this is starting to sound more and more like fuel problems.

[ivanwakeup]

care to elaborate?

just changed fuel filter and cleaned IACV. haven't taken it for a drive yet. I really should get the CEL codes, hopefully i'll do that tomorrow. a part of me just wants to order the ngk ignition coil and wires online and throw them on anyway.

[lord flashheart]

pull codes first. its too hard to diagnose with out that info.

[lord flashheart]

i just noticed your in salt lake city. i work for a shop in centerville, you are welcome to swing it by and ill take a peak at it, and pull codes.

[ivanwakeup]

dang i totally would, but centerville is a bit far, dont know if i could make it that far without it being fixed already!

codes are the way to go though. will get them pulled tomorrow, and then determine my plan of action.

[ivanwakeup]

alright update!!

got the codes pulled this morning, the list is a bit long:

-cylinder 1 misfire
-cylinder 2 misfire
-cylinder 3 misfire
-cylinder 4 misfire

-p0505, idle speed incorrect
-p0183 fuel temp sensor?
-p0102 MAF


so, i assume with ALL 4 cylinders missing the coil is toast? are these other CELs likely isolated incidents, or do they go hand in hand with the fact that it is misfiring?

[Dead91silvia]

wow... thats like the Audi A6 I just worked on... had 9 codes... haha...

Look to see if anything is corroded on the coil pack to start with. Thats easy and will take you 1-2 minutes. If it's not tossing a knock sensor code, that should be fine, but those are really easy to change out (20 min or so).

Flasheart I'm thinking is pretty close. If it's tossing multiple misfire codes, with those other codes, thats a good place to start...

[lord flashheart]

weak sauce.
i just beat an 05 LGT with like 11 codes

[ivanwakeup]

update!!!

ok, so i did the neon coil pack conversion and that seems to have helped. namely, i'm not misfiring on all 4 cylinders anymore. i drove it for about 15 minutes (fully warmed up) and no CELs came back on, so thats a good sign. however, towards the end of the drive....i was starting to lug out again. not as bad as before, but still not good.

one thing i did note was the noise i was hearing- there is a pretty substantial rattle coming from under the car, right at the cat. i was wondering- driving with the flashing CEL on for so long, is it possible that i have really damaged my cat and that is causing my problems now? i take it the rattle isn't good. how can i know for sure?

[Thomistopheles]

The infamous heat shield rattle. If you do a google search for "Subaru heat shield rattle" you'll find a few methods to fix it.

[ivanwakeup]

well, i'm much less concerned with the rattle than the performance. I take it the rattle doesn't neccessarily mean the cat is toast? its weird that i didnt get any CELs for the cat if it is gone though....

[ivanwakeup]

nevermind....took it for another drive and i'm right back to where I was.

a few more things i've noticed:

i actually can't rev over 4k. limp home, i assume?

i drove for about 20 miles just fine, then the CELs came back. about 10 minutes later i got flashing CEL too, so i assume i'm misfiring again.

ughhh this is getting frustrating.....what is it?

[Huffer]

It's going to be related to your MAF and intake.

If you clear the codes and reset the ECU, when you fire it up, the first code that appears should be the main culprit.
A poorly reading MAF or a vacuum leak will result in a misfire situation.

[ivanwakeup]

well i think i'm getting somewhere.

so i decided to throw the original airbox back on, i noticed the way i had the short ram rigged up was "less than optimal" i'll say. i'm sure it was reading a vac leak somewhere. anyway, the car is more driveable now. i can once again rev over 4k, and it seems to have some of its lost power back. i still have the same issue though, just not to as great an extent- the car gets worse the longer i drive it. the blinking CEL is not happening as often if at all now, but i still have lugging, etc.

i really am thinking my cats are clogged. how easy is it to gut them yourself? assuming i can get them off the car. If they are clogged then i guess they are shot already so might as well.

[lord flashheart]

dude swing down and ill take a look at it. diagnosing something is difficult enought, but when you are only getting the things that someone else notices its much more difficult. swing it by our shop (google metric motors centerville utah) sometime, ask for chad.

[ivanwakeup]

alright i'll try to make it there....will you be there this weekend?

[lord flashheart]

Nah I got national guard shit to do... Tomorrow or monday.