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Check engine light, code P0304

2198 Views 0 Replies 1 Participant Last post by  jimbobb
Thought mabey this might help sombody else...
For the past few weeks, car has been running rough at times (seemed to be running on less than 8 clyinders), usually after it has warmed up. Problem did not cause a check engine light. When car was started after cooling, there were no problems.
Last week, the rough running started again, this time with the check engine light. Code was P0304, cylinder misfire on #4. Thought it could be the spark plug, or the ignition coil. After disassembly, found the spark plug recess had about 1/4" of water in it. After blowing out the water with compressed air, I removed the spark plug and found the resistor end had corroded, causing an intermittant failure.
I replaced the spark plug recess oring, cleaned the resistor, and dried the ignition coil, where it contacts the resistor with compressed air/contact cleaner.
Everything runs fine now!
Most likely, water found its way in the last time engine was cleaned about a month ago.
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