Misfire codes - Subaru WRX Forum
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post #1 of 67 Old 05-19-2012, 03:59 PM Thread Starter
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Misfire codes

OK, so 02 impreza wrx, got a OBD2 reader today because i have had a CEL for a couple of weeks. the car is all stock, 100k miles. I noticed it idles just a little rough. I ran the codes today and got as follows:

P0302 Cylinder 2 misfire detected
P0303 Cylinder 3 misfire detected
P0304 Cylinder 4 misfire detected

and

P0128 Thermostat malfunction

so, i am wondering where to start, when i cleared the computer (before i ran OBD) the CEL would go off, and would not come on for anywhere between 5-20 miles, i did this 2 times to see if it would repeat. i have been wanting to get it in for a tune up, but dont have the funds yet. think it could be wires/plugs? or any other ideas? im assuming i will be getting a new thermostat, in which case, are they hard to replace? Oh, and does anybody know a good place to order a chilton/haynes for subaru? so anyways, i would greatly appreciate some ideas i can start with to try and remedy my situation!

THANKS!
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post #2 of 67 Old 05-19-2012, 04:01 PM Thread Starter
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is this the right book for my car??? its the only one amazon comes up with

Amazon.com: 2002 subaru impreza wrx haynes Amazon.com: 2002 subaru impreza wrx haynes
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post #3 of 67 Old 05-19-2012, 04:41 PM
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Whenever I floored it and got high RPM's my CEL would flash a few times then stay on when I was getting misfire codes some time back when I had mine all stock, I changed the plugs and put some fuel inj. cleaner in and no more codes. Never had therm code though?

When you reset the the CEL it takes some time for the ECU to see ther is problem and then CEL comes back.
Not sure if I just got lucky with the plugs and cleaner but try that since your gonna do a tune up anyway.


GL man.

Cobb Accessport Stage 2.
JDM ej205 swap.

Hakuna Matata.

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post #4 of 67 Old 05-19-2012, 05:07 PM
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Try this^ but if you wanna start easy try the fuel filter up front. 20 bucks. I had same codes(except t-stat code) and it fixed me up.

Kevin.
Cobb ap stage 2 ots, catless uppipe, catless turboback, Cobb Sf intake.
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post #5 of 67 Old 05-19-2012, 05:58 PM Thread Starter
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will try fuel filter for sure, you can just pull the lines even since they are under pressure right? anything special needed to be done when re-installing? since there will be air in the lines? i added some injector/intake cleaner today, havent driven it but a few miles though so i will hope that helps too.
Thanks
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post #6 of 67 Old 05-20-2012, 10:38 AM
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Nope.
Just use a rag to soak up the excess fuel that comes from the lines when you remove them from the filter for a cleaner install.
It will hesitate first start but no worries will be fine next start up.

GL Man.

Cobb Accessport Stage 2.
JDM ej205 swap.

Hakuna Matata.

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post #7 of 67 Old 05-20-2012, 11:34 AM Thread Starter
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excellent! i will be doing that ASAP then
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post #8 of 67 Old 05-20-2012, 02:20 PM
 
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Loosen your fuel cap before you remove the line. That will relieve pressure, less gas mess.

Cullen
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post #9 of 67 Old 05-20-2012, 03:07 PM Thread Starter
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OK, just replaced the fuel filter. Started her up and i can bet the misfires are still there, the idle is a little rough, its not bad, but its there. No CEL yet... but like i said before that seems to take a while to come on. any other suggestions? or should i try and wait for the CEL and re-run the scanner? i will anyways if the light xomes on. in the meantime i guess i will start trying to find a decent mechanic to do a tune up
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post #10 of 67 Old 05-20-2012, 03:35 PM Thread Starter
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does anybody think it might be my MAF? i might get some cleaner ant try that, but it seems strange that it would only misfire 3/4 cylinders... or am i wrong and that is normal
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post #11 of 67 Old 05-20-2012, 05:57 PM
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Did you try replacing the plugs?

Cobb Accessport Stage 2.
JDM ej205 swap.

Hakuna Matata.

Chuck.
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post #12 of 67 Old 05-20-2012, 06:43 PM Thread Starter
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No, i havent done plugs yet, did just clean the MAF and no change there either. anybody know of a good tune up shop? Im in San Jose CA. im not sure if the big companies would be good or not, like AAMCO, worth a look i guess
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post #13 of 67 Old 05-20-2012, 07:46 PM
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Try resetting the ecu. Undo the positive battery terminal, and pump the brakes a few times to finish off the residual energy that's left, let it sit for a bit then try starting it up. I had to reset my ecu after fuel filter change. The ecu had learned bad readings for it(fuel filter) being bad for a while. It took me a solid month of troubleshooting to check that. After a drive to okc and back(about 250miles) it had re learned back to where it needed to be. Been fine ever since. I did have the ap to help with the ecu resets and monitoring the dam and such... I was at a dam of 3(which on the older cars you want to be at 16), so my car was not happy at all. After The reset it flirted around 10-14 for about 70 miles then finally shot up to 16 and stayed there. Worth a shot at least, and you will prob get a temp power boost before the ecu learns itself back to where it needs to be.

Kevin.
Cobb ap stage 2 ots, catless uppipe, catless turboback, Cobb Sf intake.
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post #14 of 67 Old 05-20-2012, 10:08 PM Thread Starter
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i disconnected the negative and hit the brakes, but i didnt really let it sit fo long, maybe 2-3 minutes. is that the same or should i try the positive too? what is the "dam" you are talking about?
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post #15 of 67 Old 05-20-2012, 10:39 PM
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Dynamic advance multiplier, it just a number rating the ecu give for how "happy" it is. Unless you have a way to monitor live data(Cobb accessport, or some form of data logging) you won't be able to see it. I'm not sure on how long you have to let it sit. I would guess as long as all the dash lights go off, including the odometer it would work. Anyone else know that??? This is one feature that I absolutely love my ap for.

Kevin.
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