2004 WRX misfire in cylinder 4 and sometimes 2.

Asked by Jan 24, 2013 at 03:54 PM about the Subaru Impreza

Question type: Maintenance & Repair

2004 wrx 177,000 miles.
Cylinder 4 misfires at low rpm. CEL blinks at low rpm then goes out at around 3000. Will do this a few times before cel stays on. Have replaced coil packs and plugs. Bought a scanner and everytime cel is on its for a cylinder 4 misfire. Compression in cylinder 4 is also about 20 psi lower than others 120 vs 140. Car runs well, no backfires . doesnt smoke or burn oil. Mechanic thinks it may be a bad exhaust valve.
Your thoughts?
Worth fixing?

5 Answers

'Worth fixing' is partially a personal rather than a pragmatic question. Depends on cost, and at 20psi lower, I think no worries, I wouldn't put a dime in it at this stage, might as well do a valve job if head is coming off not one exhaust valve, and only slightly bad at that, Nah. Drive 'er to the moon

1 people found this helpful.
35

I had that issue, then it got worse and would misfire constantly, a new O2 sensor sorted that out. I wouldn't worry about doing a valve job unless you were seeing a number under 100psi.

1 people found this helpful.
475

100 bucks says you have a bad ringland. Oil will seep past the rings and lower the octane of the fuel, which causes knock and misfires. Shortblock will need to be rebuilt, the issue will only get worse. It is better to do it now while you still have a usable block.

Hey did u ever find out what was causing ur miss fire I have the exact same issue going on and I can't figure out what's going on with!!

??

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