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Random misfires on all cylinders

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Old 10-26-2006, 08:45 PM
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Default Random misfires on all cylinders

Guys,

My new 408 has random misfires on all cylinders...is this common/acceptable? In other words, does GM expect/account for these with their EFi PCMs?...or do I need to investigate this further? What are some common causes for random misfires on both banks?

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Old 10-26-2006, 09:16 PM
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On my truck (04 silverado Z71) I had an 02 goiing out with was dumping too much fuel causing misfires... How old are your 02's?
Old 10-26-2006, 09:48 PM
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..they are stock O2s from my 2000 Silverado Z71....I thinkthis might be a good starting point....did you disable the downstream ones?....I'd prefer to buy just 2 (upstream) if I can.......
Old 10-26-2006, 09:49 PM
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How did you know it was the O2 sensor going bad?....
Old 10-26-2006, 10:25 PM
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Originally Posted by Stroker2112
Guys,

What are some common causes for random misfires on both banks?
Large cams with stock misfire tables.

i.e. you need to edit the misfire tables in the PCM
Old 10-26-2006, 11:06 PM
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MY bud tapped into it with EFI Live..
Old 10-27-2006, 12:32 PM
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Make sure the front o2 sensors are not REVERSED.. mine were and I had similar problems!
Old 10-28-2006, 12:49 PM
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I'm just going to buy 2 new ones and see if that solves the misfire problem....

Thanks,

Stroker2112
Old 10-29-2006, 09:38 PM
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did that fix the problem cause i think i have te same problem and im hoping its jsut the bad o2 sensor
Old 10-30-2006, 03:25 PM
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I just got the O2 sensors a few minutes ago...will put them on after work to see what happens....wish me luck......
Old 10-30-2006, 08:45 PM
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Good luck!
Old 10-30-2006, 10:19 PM
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If it works, it might take several cycles to get rid of the SES light.. I know it did on the Silverado.. But, I bet you can feel it right away if it works though.
Old 11-04-2006, 08:53 AM
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Yes, it worked right away....drove it for about 30 minutes...then lost 2nd gear. I'm days away from ordering a new FLT tranny. Curious, as the car sits in the drive way, it won't start anymore...turns over but won't start. Would the new 02s have thrown the base tune out of whack?......Any ideas on where to start with this new issue while I wait for the tranny?

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