gm junk 06 cobalt 2.2 misfirre

after replacing ckp sensor (crankshaft position sensor) car no longer dies but still missfires only on cold starts. never at the dealers though. codes p0300 p0336 p0106 before i replaced sensor

Reply to
nate
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So the P0300 is a 'random misfire', which based on your limited information, sounds plausible. P0336 does not mean 'bad crankshaft position sensor' however, and if you replaced the sensor on this code alone without diagnosing the system you may have thrown parts into the mix unnecessarily. P0336 is a -bad signal- from the CKP, but not a LACK of signal.....which could be due to a bad sensor, or a damaged pickup wheel(incorrect gap, physical damage to the prongs), or damaged/ frayed wiring in the loom somewhere.

P0106 is an interesting code because it indicates a problem with the MAP sensor. A problem in this area could throw the mixture off enough to create the right conditions for both a misfire -and- a bad signal from the CKP, after all, if the engine isn't firing correctly and the ECM expects regular pulses from the CKP, it may not get them if the mixture is going far too rich or far too lean.

If it was my car, I'd look into the P0106 first and troubleshoot that initially. The fact that you said it only misfires on a cold start is a good clue. I'd check the connections to the MAP, maybe take it out and clean it or swap it for another. You didn't mention how many miles are on the car or any other information(Has it been overheated? Crashed? Has it gotten regular maintenance?). All of those could play into sensor failure. Hell, it could be dirty fuel injectors...or a bad plug. Hence the question about maintenance and mileage.

One thing you need to keep in mind is that an OBD-II code indicates a problem in a -CIRCUIT-, not necessarily a sensor. I'd hedge a bet that you'll find a problem somewhere in the air/fuel metering system that when repaired will cure the other two codes.

I've driven cobalts several times and found them to be nice cars that have a bit of pep. If you're calling it junk, maybe you should just trade it?

Good luck with it.

Chris

Reply to
Hal

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