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Old 09-11-2010, 04:14 PM   #1
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Bad O2 sensor cause misfire?

Can a bad o2 sensor cause misfire? I had a O2 sensor bank 2 code that I cleared and then once I cleared it I got Misfire in bank 2 , cylinder 4 , 5 and 6. Coincidence or is something else up with my car? I am going to try to replace the O2 sensor first and see if that helps, but if anyone else experienced similar problems or have experience with misfires, please let me know
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Old 09-11-2010, 05:20 PM   #2
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When troubleshooting EFI problems you must keep in mind that the error codes are simply pieces of information and not gospel in terms of what the fault is.

Multiple misfires on the same bank as the O2 sensor error tells me that the O2 sensor is probably fine and that code is being caused by the misfires.

If your pre-cat O2 sensor is bad you will get lean/rich error codes not cylinder misfires. Misfires are electrical in nature. Start your search with the things that create the spark fire sequence and spark.
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Old 09-11-2010, 05:43 PM   #3
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Quote:
Originally Posted by landrovered
When troubleshooting EFI problems you must keep in mind that the error codes are simply pieces of information and not gospel in terms of what the fault is.

Multiple misfires on the same bank as the O2 sensor error tells me that the O2 sensor is probably fine and that code is being caused by the misfires.

If your pre-cat O2 sensor is bad you will get lean/rich error codes not cylinder misfires. Misfires are electrical in nature. Start your search with the things that create the spark fire sequence and spark.
So spark plug, coils etc? The only reason why I don't think it is the spark plugs is because its unrealistic that all 3 plugs and coils on the same bank went bad at once.

I did have a pending P1133 and P1126 as well before I cleared it. I actually just did a search and most people are saying clean the MAF. I am going to try this next, This is going to surprise me if a simple MAF problem caused about 8 codes to trigger on my car
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Old 09-11-2010, 05:55 PM   #4
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I would bet you $100 that it is not the plugs. I would bet you the same amount that three coils did not go out at the same moment either. And your MAF is not going to cause a misfire and if it could (but it can't) why on only one bank and not the other.

Like I said these are all symptoms. What chain of events could cause them all to happen? What are the things that tell the ignition system when to fire? Crank position sensor? Cam position sensor? This is where you start.

Have a good Porsche mechanic look it over for you.
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Old 09-11-2010, 05:59 PM   #5
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I would bet you $100 that it is not the plugs. I would bet you the same amount that three coils did not go out at the same moment either. And your MAF is not going to cause a misfire and if it could (but it can't) why on only one bank and not the other.

Like I said these are all symptoms. What chain of events could cause them all to happen? What are the things that tell the ignition system when to fire? Crank position sensor? Cam position sensor? This is where you start.

Have a good Porsche mechanic look it over for you.
Thanks,
I didn't think about it that way. I am going to bring it to a porsche mechanic, probably save me a lot more time/trouble
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Old 09-11-2010, 06:10 PM   #6
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Smart choice, replace only the part/parts that are causing the problem.

If it was a GM and parts are cheap as dirt then who cares but Porsche parts are too pricey for the shotgun approach, besides it is much more fun to actually figure out what it is doing.
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