Just had my car autotapped and to my disbelief my #2,4,6, and 8 cylinders are all misfiring! Changed plugs the other day and all passenger side were covered in soot or carbon (unless their the same) thinking this would fix the problem. Also my Bank 2 sensor 1 is reading only between 45-60Mv at any power level (easy fix I assume passenger side 02) but my questions are, what could be causing my passenger side plugs to foul (besides the obvious disconnect, reconnect harness which i have done) and is the bad O2 the result of my passenger side fouling? Please help.

 

Wonder if something is bad inside the pulse damper,
choking off fuel. Other bankwise possibilities are loss
of the injector ground (?) or coil pack wiring. Unburned
air/fuel contains plenty enough oxygen to peg the
sensors low. An old-school inductive clamp timing light
will tell you if you are throwing spark, you might want
a "noid light" from AutoZone to check injectors' pulse
presence. Once the O2s and plugs are fouled you could
get into a death spiral situation but probably should go
thoroughly through the basics before throwing parts
at the problem.

 

If all the passenger plugs were black and sooty, then those cylinders are RICH. If the O2 sensor is reading 45-60 mV, then its reporting to the PCM that bank 2 (passenger side) is running LEAN. So if the O2 sensor is telling the PCM that bank 2 is lean, then the PCM is going to keep adding fuel until the sensor starts switching rapidly between 45mV and 900MV. If for some reason the sensor or signal wire is shorted, causing it to stay low, the PCM will eventually keep adding fuel until its maxed out, which is probably causing a Rich Misfire on bank 2 (cylinders 2,4,6 & 8). Unplug the O2 sensor (bank 2 sensor 1) and see of the mV goes to 450 (or near 450). If it stays around the 45-60 mV, then the signal wire is shorted or the PCM is bad. If it does go to the 450mV bias voltage, then the signal wire and PCM is good, and we can then suspect a bad O2 sensor, since the plugs indicate that bank is rich, despite the O2's lean reading.

 

Thanks for the quick replys! It really sucks being here in the UK cause there are no GM dealers and I have to deal with UK mechanics that don't know what a Gen III motor is! I'll try unplugging the sensor tomorrow and see what happenes, that does make sense, otherwise I'm totally on my own!

-Travis

 

Ok, this gets weird. I did the obvious and changed my O2 sensor out with a new one that I had for a spare. Swapped that out hooked up autotap and started it up. For about 10 min everything worked great then.....It fell back between 0-60Mv and wouldn't go above that and my RT side started to misfire again I ohm checked my harness and everything checks ok. I'm on the verge of losing my mind because no matter what happens I don't have a GM dealership or anyone with GM knowlegde to hep me out over here. I logged this last one which shows it working fine then falling if anyone could take a look at it for me. Any help would be greatly appreciated!

-Travis

 

swap coil packs to the driver side and see if it follows or stays.

 

Why don"t you swap the drivers side 02 into the passenger side bung instead of using an old spare o2 in that bank? ...you now that o2 is good becasue the driver's side bank is not running lean...

...you have strong spark; right? How did you test the ignition spark?

 

If only you were nearer I could have given you a hand, I have HP tuners. I'm near Portsmouth in Hampshire (South coast of England)

You may have a bad O2 sensor, PCM adding extra fuel because it thinks its running lean.

 

I may have to look you up if your willing to give me a hand! That wouldn;t be to bad of a drive...how far from Gatwick are ya?

-Travis

 

have you cleared the current codes? i dont think the o2's would cause a misfire..not on all cylinders..would it?

 

Well, I have changed my 3rd O2 sensor (Walker) and it has done it again (Yes, I have cleared the codes everytime). Car is misfiring on the even cylinders as well as putting out the code for low O2 voltage (stays between 10-60Mv at any rpm) I have the extended warranty so now I have to throw all my stock exhaust parts on so I can take it to a company through GM (that I spent 3 hours on the phone to find out there was one)t hat will try to figure it out. Any ideas? The only thing I haven't done is swapped the coil packs around which I may do this weekend for just a gee whiz thing. But I need this car to get to work and I'm screwed if I don't get it fixed, not to mention the long term effects this may have.

-Travis

 

eliminate possibilities. you've eliminated o2 sensors as the possibilities. move on to the next. swap coils and see what happens. you might want to totally clear the puter by unplugging it, not just clearing codes.

 

its not hard to swap the coil packs..its easier than doing the plugs! do that, then clear the codes and see where the pop up next.

 

Did you ever solve this problem? Currently having the exact same problem and having the hardest time trying to figure it out.

 

PM the OP. He's still around.

 

alright will do, thanks 😁

 

Having this exact problem. Did you ever get a reply from op?