2002 Subaru Impreza engine misfire

JDWRX

MEMBER
2002 SUBARU IMPREZA
4 CYL
AWD
MANUAL
140,000 MILES

After driving the car hard, the check engine light started flashing, so I got home and scanned the code. I got a misfire in cylinders 2 and 3. I have replaced the spark plugs with oem ones, I have also switched the coils from a good cylinder with a bad cylinder, and I have checked the fuel injectors, which I also interchanged, but I continue to have misfires in those cylinders. I'm not sure what to check for next, so I am asking for some advice. THANKS

9 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Check the compression for 3/2 cylinder

Misfires can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.

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Sunday, March 16th, 2008 AT 7:05 PM

JDWRX

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Ok thanks. Since im kind of newbie to cars, what will a compression test determine?

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Sunday, March 16th, 2008 AT 7:09 PM

RASMATAZ

MECHANIC
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It will determine if that cylinder is leaking compression valves/rings not producing its share of power output the CPS wil sense it and reports this as misfire to the computer.

Recheck the coils -cyl 1 and 2 shares the same coil

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Sunday, March 16th, 2008 AT 11:08 PM

JDWRX

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I ordered a compression tester, which will be arriving the next couple of days. I will probably do the compression test this weekend because of work, but I will get back to you with the results as soon as I can. Thanks

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Monday, March 17th, 2008 AT 7:16 PM

JDWRX

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I did the compression test on cylinder 2 and I got 150psi and the same for cylinder 4. I only had time to do those two, but I think they look ok, right?