P0300 - Misfire Code...caused by O2 sensor?
09-17-2007, 01:04 AM
#26
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09-17-2007, 01:50 AM
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I have a question regarding misfires. Do you guys think a ingall's torque dampener or solid motor mounts could cause a misfire . I have a random misfire across all cylinders but only when im at idle , or up against the motor when slowing down . Never when on the gas . My idle is kinda rough , you can hear a random puff at idle . Mod's in sig . Thx
09-17-2007, 07:14 PM
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Dont sweat it dude, not really "arguing" just trying to explain how it works is all...
The "basic" criteria is linked to the Federal Tes Procedure (FTP) and therefore an OBDII "standard" But GM DOES do a few things differently with respect to the misfire accumulators and the CKP velocity table that is used to establish the intensity of the misfire (as this affects the behavior of the MIL (flashing) and Type A/B states)
There's a real good explaination for this in the GM OBDII training texts. Are you a member of the i-atn? If so check out the GM section in the Techncial Resources section
Regards
WopOnTour
The "basic" criteria is linked to the Federal Tes Procedure (FTP) and therefore an OBDII "standard" But GM DOES do a few things differently with respect to the misfire accumulators and the CKP velocity table that is used to establish the intensity of the misfire (as this affects the behavior of the MIL (flashing) and Type A/B states)
There's a real good explaination for this in the GM OBDII training texts. Are you a member of the i-atn? If so check out the GM section in the Techncial Resources section
Regards
WopOnTour
I have a question regarding misfires. Do you guys think a ingall's torque dampener or solid motor mounts could cause a misfire . I have a random misfire across all cylinders but only when im at idle , or up against the motor when slowing down . Never when on the gas . My idle is kinda rough , you can hear a random puff at idle . Mod's in sig . Thx
if your MAF is mounted improperly then it could cause the problem. We have really sensitive MAFs on these cars. And there's been alot of problems with aftermarket cais because of it.
Are you actually getting misfires or is there just a code for it without the engine running roughly?
Last edited by Novajoe; 09-17-2007 at 07:14 PM. Reason: Automerged Doublepost
09-18-2007, 12:23 AM
#30
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solid motor mounts aren't going to cause a misfire. It doesn't actually cause more vibration on the motor, just allows the vibes to be transferred to the frame. You probably really do have a misfire, and should get it checked out. Did the problem start directly after you added any engine mods? Or did it just start out of the blue. If it just kinda started then I'd go through the regular check procedures. Make sure your plugs are good and that you don't have any ign probs. Check that your fuel pressure is good and that all injectors are firing properly. Check that your timing is good, etc. The problem's going to be in one of those areas and should be pretty ovious as long as you've got a hard code.
09-18-2007, 01:53 AM
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Thats one of the problems, it hasn't set a code ....ever. The way it started i guess was at idle i would hear a little puff here or there , kinda like a miss . After listening to other people's exhaust clips i've noticed alot of their cars do it too .... but i have access to my dealers tech2 so for giggles i logged a 5 mile drive and saw them all across the board . Thx for the help Rukkee
Also even though your car might be misfiring, it would throw a code if it was anything serious. I think our pcm allows for up to a 3% misfire before it actually throws a code on it... but don't quote me on that.
Holy jesus...I don't check this thread for a few days and its 2 pages long.
WopOnTour: You seem to know your stuff when it comes to this issue. In case you don't know, I am the OP of this thread...If you say the O2 sensor likely was ruined as a result of the misfire....what would you say caused it?
Some more background info...
- My rotors had some high spots on them....I wouldn't say the warping was severe...just to the point of being annoying.
- I never once threw the code until I installed the LSJ Header/DP/Catback. 5 Minutes after leaving the garage, it threw that code.
- I could always smell unburnt fuel in my exhaust fumes while the CEL was on.
Been driving since last week when it was fixed and it hasn't come on since and the nasty exhaust smell has gone away as well.....SO..based on what you said earlier, the bad rotors usually throw a false misfire code but since I could smell the unburnt fuel in my exhaust, I would assume my code was not a false and it was actually misfiring..essentially ruling out the rotors as the cause. Reading the potential causes you listed above, all my wheels are balanced...it was done not 1000KM prior.
Nothing else listed in your post was worked on or replaced on my car, just the O2 sensor.
So...based on all of that, what else could have caused the problem?
WopOnTour: You seem to know your stuff when it comes to this issue. In case you don't know, I am the OP of this thread...If you say the O2 sensor likely was ruined as a result of the misfire....what would you say caused it?
Some more background info...
- My rotors had some high spots on them....I wouldn't say the warping was severe...just to the point of being annoying.
- I never once threw the code until I installed the LSJ Header/DP/Catback. 5 Minutes after leaving the garage, it threw that code.
- I could always smell unburnt fuel in my exhaust fumes while the CEL was on.
Been driving since last week when it was fixed and it hasn't come on since and the nasty exhaust smell has gone away as well.....SO..based on what you said earlier, the bad rotors usually throw a false misfire code but since I could smell the unburnt fuel in my exhaust, I would assume my code was not a false and it was actually misfiring..essentially ruling out the rotors as the cause. Reading the potential causes you listed above, all my wheels are balanced...it was done not 1000KM prior.
Nothing else listed in your post was worked on or replaced on my car, just the O2 sensor.
So...based on all of that, what else could have caused the problem?
Did you check the code as soon as you left the garage? The O2 could have been damaged when the parts were swapped. You might have not even been throwing a misfire code until your rotors got warped.
Last edited by Novajoe; 09-18-2007 at 01:53 AM. Reason: Automerged Doublepost
09-18-2007, 04:24 PM
#32
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well when your O2 sensor goes bad, your car has no way to check the oxygen levels of the exhaust. So it tends to throw more fuel in than usual... making you run rich. You probably don't smell the fuel in the exhaust as much anymore because you now have a properly working O2 sensor.
Did you check the code as soon as you left the garage? The O2 could have been damaged when the parts were swapped. You might have not even been throwing a misfire code until your rotors got warped.
Did you check the code as soon as you left the garage? The O2 could have been damaged when the parts were swapped. You might have not even been throwing a misfire code until your rotors got warped.
09-18-2007, 04:32 PM
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well I don't know what to tell you then. Wop just proved that a bad O2 can't cause a p0300 on our cars. If the code hasn't come back since you did the repairs then I would chalk it up to the rotors.
09-18-2007, 07:21 PM
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well the first thing I would look at is your k&n filter. I know that on the ls1s the oil on them has a tendency to screw with the maf sensor and throw the readings off. Try cleaning off your maf sensor and running the car with a dry-flow filter on it and see if the misfires stop then.
09-18-2007, 08:14 PM
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it could have something to do with the stage 2. I've never datastreamed a stage 2 car so I wouldn't know. But then I've never datastreamed a stock ss/sc either. I'll have my friend with a stock ss/sc come over and datastream his sometime and see what I get.
09-21-2007, 02:16 AM
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hey I datastreamed my friends ss/sc. WITH his aftermarket intake on he gets small random misfires. On his stock intake he doesn't have them. It looks like the maf doesn't like the change in airflow characteristics the aftermarket intake provided.
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