1998 Subaru Legacy Check Engine P0304

Tiny
ANOMICS
  • MEMBER
  • 1998 SUBARU LEGACY
  • 4 CYL
  • AWD
  • AUTOMATIC
  • 159,000 MILES
I'm getting a check engine code P0304 for a mis fire in cylinder 4. I have replaced the spark plug, wire, and tested the coil with meter and all is fine.
I could tell from engine vibration if it was mis fireing. At first it was very sporadic. It would be fine for a day and then it would mis fire again the next day, and would work fine for half of the next day. Now it has gotten worse and I believe cylinder 4 is not working at all because engine vibration at idle is really bad(whole car shaking) and the car is on the edge of stalling at idle. I just don't know what to do next but to take it to a professional repair place and spend buku bucks just for them to spend hours trying to find the problem and replacing all my electrical, again. Please help!
Sunday, May 10th, 2009 AT 2:38 PM

1 Reply

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Misfire on a specific cylinder should prompt you to check the sparkplug/compression/injector for that 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, May 10th, 2009 AT 3:52 PM

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