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Old 02 Apr 2019, 09:57 am
inertian inertian is offline
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Join Date: Jan 2015
Location: Lindenhurst, NY
Posts: 44
Default What's Causing Misfire and CEL?

2004 PTCruiser Turbo Lite, 114K miles.

Stumped by the cause of a recurring P0302 code (misfire cylinder 2) and CEL light.

Sequence of events:
  • Normal cold start
  • Drive a few minutes and while stopped at first stop sign or red light idle gets rough, CEL flashes,throws code P0302 (via UltraGauge).
  • CEL light comes on steadily*
  • Continue to drive without issue - no additional codes or rough idle, just CEL

A few years back I replaced the upper and lower manifold gaskets to address a similar misfire condition. I have also replaced the stock wires with MSDs, fresh Champion copper plugs and most recently, replaced the head gasket due to oil on the spark plug tubes.

My mechanic just scoped the engine, no oil or signs or burnt valves.

We both checked that good spark is getting to the plugs.

Previously we swapped plugs and wires but the problem stays with cylinder 2.

Possible causes:
Burnt valve - scope shows no evidence, and wouldn't the problem be continuous?

Bad valve seats/guides - could be effected by temperature, but no telltale blue smoke at startup

Bad fuel injector - plenty of power and decent mpg, worth it to pull the head and check?

Suggested Actions:
Add fuel system/injector cleaner - done, no change

Replace original coil pack - would think the problem would be worse once the coil pack gets hot vs only when its cold.

Check/replace ECM - replaced original ECM a few years ago when I couldn't disengage the Security system (car wouldn't start or take reprogram)

Other suggestions welcome.

*If I clear codes by disconnecting battery, the CEL may not come on steadily the first time it flashes.
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2004 Chrysler PT Cruiser Limited Edition Platinum Series 2.4L 4cyl Turbo
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