Random Misfire Car Shaking Bad.

[BOOSTED20PSI]

Ok So I Have A 02 Wrx With Accessport Stage 2 Pretty Much Stock Besides Stage One Clutch And Tanabe Downpipe Back Exhaust. Im Getting A Random Misfire When Im In 5th At Full Boost The Cel Will Flast A Few Times Then Go Off Without Me Having To Clear It. You Cant Tell A Difference In The Power When The Code Is Thrown. I Have Changed Spark Plugs Fuel Filter And Checked Coil Packs All Are Good.any Ideas??? Also If I Let My Car Idle For 10 Min Or So I Get A Horrible Shake Through The Whole Car Like Its About To Rattle Apart. I Cut The Key Off Imidiatly When It Does This And Start It Back Up And The Shaking Is Gone. It Doesnt Throw Any Codes And Rpms Are Not Affected Kinda At A Loss Here Any Help Would Be Aprriciated. Thanks

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[badmannersgod]

Try cleaning out your MAF sensor, have you been able to at least read the code to know which cylinder its coming from?

[BOOSTED20PSI]

I cleaned the maf then noticed it wasn't all the way screwed down the collar the screw goes into stripped out of the air box hopefully the leaking air was the problem hasn't done it since the fix

[BOOSTED20PSI]

Still having a random mis fire any other ideas

[BOOSTED20PSI]

Originally Posted by badmannersgod

Try cleaning out your MAF sensor, have you been able to at least read the code to know which cylinder its coming from?

AND NO I HAVNT IT DOESNT STAY ON IT FLASHES A FEW TIMES,I THINK 4 TIMES, THEN DISSAPEARS.

[wrxlaunch]

Flashing cel is real time misfire. What is max boost in 5th? And why not just downshift?

[BOOSTED20PSI]

Max Psi Is 18 And I Do Downshift But I Have To Shift To 5th Eventually

[ezil71]

How did you check the coil packs?

I had misfires on my 03 a while ago and couldn't find the cause. I ended up replacing all the coil packs and haven't had a problem since.

If you haven't run any seafoam in a while, that can help clean things out.

Could be one of the coil packs isn't fully seated? The one on the passenger side that has the bracket on it would be the first one I'd look at. Make sure the bracket is really seated properly, not just 'kinda' seated properly.

When did you last change the plugs?

[kelsyf13]

I was having random misfire on all cylinders for a long time, when cruising in 5th and sometimes at idle the cel would flash, swapped plugs, coil packs, maf, cam/ crank sensors. Ended up being #3 injector might be worth taking a look at them. It also shook quite badly at idle.

[ogboot]

Sucks that you're misfiring. You should really be moving before you go into 5th on the 5 speed. Like hauling ass. 4th gear takes you over 110 at least. What rpm are you shifting into 5th, and at what rpm are you getting the cels?

[BOOSTED20PSI]

i bought all new coil packs changed them out and the spark plugs less than a month ago i checked and made sure they were seated right also i have ran seafoam through my vac lines, fuel tank, and oil then changed the oil bout 50 to 70 miles after adding it. the oil was acutally pretty clean. Im starting to lean toward a injector problem jsut doesnt make sense that it is on all cylinders at one time.

[BOOSTED20PSI]

and ogboot i will shift out of 4th anywhere from 5500 to 6500 and it flashes normally around 5 after full boost has been set for 3 to 4 seconds also it idles fine besides the normal shimmy of a subi unless i leave it idleing for a good period of time then it starts violently shaking like the flywheel is loose thats the best example of how it feels.but i took the starter off and didnt feel any play in the flywheel.

[kelsyf13]

Mine was all cylinders too and I thought the same thing. I think it was the rough idle causing the engine to detect a misfire, worth checking fixed my problem.

[bushflyr]

Bizarre. I just started having a similar problem a couple days ago too.

1. Going around a 60mph onramp, WOT in third I felt a lurch and got off the gas. No CEL.
2. Shortly thereafter I did a WOT pull at about 55mph in third. The boost appeared to pause going through 14psi then continued to build. Felt the lurch again at 20psi and CEL began flashing for about 5 seconds then gone. NO STORED CODE.
3. I just reflashed my base map (protune) and tightened the intake hose clamps that I could reach. Went for a 2nd gear pull and got violent lurching going through 7psi or so. It feels like ALL CYLINDERS are missing at the same time. Flashing CEL for 5 secs or so Then gone.

I'm almost wondering if it could be clutch slip and grab causing the issue. When I started up cold today my clutch judder was twice as bad as it's ever been. Off to clean the MAF when it cools down.

[Wills03rexwagon]

if possible try switching your coils around and see if the miss fire follows, if it follows you know your having a spark issue, if it stays I would check the injector for that cylinder

[greenplates]

spark or fuel.

coil or injector.


try those first

[BOOSTED20PSI]

swapped coils around and made no difference

[animalcrackers]

Had the shaking and flashing cel problem. Turned out to be too big of injectors. Went down in size, rescaled mac, and boom fixed

[animalcrackers]

maf**

[BOOSTED20PSI]

Maf Is Freshly Cleaned Along With Every Sensor I Could Clean And Its Stock Injectors Is It Possible For It To Work Itself Out Of Tune???

[animalcrackers]

Are you on an accessport tune, open source or what?

[BOOSTED20PSI]

Yes Im On Accessport STAGE 2 It Was Tuned On A Mustang Dyno In Nc Before I Bought It

[kelsyf13]

I still say injectors, start with the basics before blaming tune.

[Jeffman44]

Should be running colder plugs if you.aren't already. The std Heat range will get really hot at full 5th gear load on a long pull. Hott enough to cause pre igniton - misfire.

[greenplates]

Stage 2? Bring it to a tuner bro