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Missfire help - Updated!

1661 Views 15 Replies 5 Participants Last post by  Theminidude, 
T
Hello, I have an 02 forester s with the 2.5rs motor. A while back it started miss firing and running really rough. I replaced plugs, coil, and wires, and I put probably 600 miles on it and it came back I don't know what to do. Any suggestions?
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2.5x_sleeper
Do you have a lit CEL? If so, what codes do you have? :confused:

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Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
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T
I have no clue on the codes and the check engine light is on but not flashing it was doing that the last time and I'll set it up later
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2.5x_sleeper
If the CEL is lit, you have stored error... malfunction codes. If the CEL is flashing, that means the problem is happening at moment & that's serious! :icon_eek:

Get the CEL code read, which will give you a clue on where to start the trouble shooting. :wink:

Most auto parts stores will read the CEL code for you at no cost.

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Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
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T
I haven't been able to drive it anywhere or get the codes scanned I know it's in cylinder 2 for a fact

It was in cylinder 1 the last time

it smells like gas really bad when it runs if that helps too
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Kevin
"Somehow" you will need to get the codes read otherwise you're shooting in the dark and almost impossible for others to help you with the issue. Perhaps you can get a OBDII bluetooth adapter that plugs into the OBDII port under the steering wheel then get a smartphone app to connect and read the codes?

The adapters are cheap, around $25
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T
update I get paid tomorrow so I can buy a scanner but I listened to all my injectors and all four are firing and I replaced plugs again to see if that would fix it still miss firing with the flashing check engine light
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J
Not sure if this works on US vehicles, but there is a way to read the fault codes by connecting the green connectors under the steering wheel area: http://www.scoobypedia.co.uk/index.php/Knowledge/ReadingECUCodes
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T
Sorry for the very late response it turned out to be the ignition coil again thanks for all the help
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T
Hello I've posted before on here asking for miss fire help. I have a 2002 Forester s, and if I remember right the code is p0302 for miss fire in cylinder 2. It only seems to miss fire after the engine has started to warm up and it's really noticable at idle. I've replaced plug wires, plugs, and the coil, as well as replacing the pcv. I have also checked the grounds coming off the battery and cleaned them up. I've taken it to a shop where they tested for vacuum leaks, they moved the plugs and plug wires around, and did a compression test, and the miss fire never moved. The mechanic said the car had compression but told me its a mechanical miss fire. He said there is something wrong with the camshaft or valve. But wouldn't that show up in the compression test? And on top of that it was going to to cost 2200 to remove the head and check it out. What do I do? And do you guys have any advice, I don't know anymore and I'm running out of ideas.

and a little more information about my car it has 148 thousand miles, k&n high flow filter, full exhaust tsudo 2.5 rs uel headers and high flow mid pipe as well as the tsudo 2.5rs catback.
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2.5x_sleeper
@Theminidude your new thread has been merged with your existing thread. No need to create a new thread when you already have a thread on the same subject. It's better to keep all the troubleshooting information together. :wink:

Your previous post said the problem was another bad coil pack? :confused:

Did your mechanic give you the results of the compression test?

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
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T
yes the coil fixed the problem that time and the mechanic said it had good compression.
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2.5x_sleeper
Curious that you had 2 bad coil packs! Were the replacement coil packs factory/OEM or aftermarket? I have read where aftermarket coil parks are problematic. Members have had better results with factory/OEM, new or used.

When your mechanic did the engine pressure testing, did he give you the pressure reading of each cylinders? :confused:

Also... is the CEL - check engine light lit now? If so, what codes are stored?

If the CEL code is a P0302, take a look here: P0302 SUBARU - Cylinder 2 Misfire Detected Check out the "Possible causes".

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
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T
Thanks for the help I'm going to rent a compression tester and do it myself and the coils were replacement ones I believe the plug wires I had were trash because the right bank of my motor had significantly higher resistance and cylinder 2 and 4 were dead when I took it to the shop last. I have new ones now
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Sackett
Occasionally, a valve guide can break loose and cause a intermittent misfire

Sent from my SAMSUNG-SM-G935A using Tapatalk
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T
Sad to say after all the testing I did it turned out to be piston rings. :(
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