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Discussion Starter · #1 ·
Spark plug Auto part Automotive ignition part Automotive engine part Brass
Auto part Spark plug Close-up Still life photography Automotive engine part


Every 30K miles or so ny 2002 wrx gives a P030x code and I have always been able to fix it by replacing the plugs, until now.

This time after replacing the plugs, the car still gives the P0302 code, along with vibration and loss of power. Actually it alternates between this error condition and driving fine at random.

Does the fact that it sometimes drives fine eliminates some possible causes mentioned in the misfire code sticky thread?

I attached photos of plug #2. Does it tell anything useful?
 

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I agree that plug looks good. Can't say much about the misfire except to ask if you changed out the wires also? Wires "flop" and even get wet if they have hairline cracks; that "may" explain randomness.......
 

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Discussion Starter · #4 ·
If I take the car to a subaru mechanic, is it possible they have a better diagnostic tool (perhaps a subaru-specific ODB 2 scanner) to pinpoint the problem, or are they just going to go through the list of possible causes in the misfire sticky thread?

The error is always P0302.

If I leave the spark plug connected to the coil and hanging outside the engine and start the car, would that be a good way to see if there is spark?
 

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Discussion Starter · #6 ·
I swapped the #2 and #4 coil, hoping the error would change from P0302 (cylinder 2 misfire) to P0304 (cylinder 4 misfire). Surprisingly, the car runs perfectly fine since then.

I now believe the real problem is poor contact between the coils and the wires. I recall when disconnecting the coils, the connector detaches way too easily after pushing the release tabs. I think the process of swapping coils caused the poor contacts to become good again, at least temporarily.
 
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