o2 sensor/cylinder misfire?
Posted May 4, 2007 at 10:14 am
So the dealer tells me that they're reading a misfire in the bank 6 cylinder. That the unburned fuel is going down the exhaust, and that's affecting the o2 sensor. He recommends getting all 6 plugs and wires replaced (they only have about 29k miles on them), and then obviously swapping out the sensor. He'll cover the sensor under my warranty, but wants $300 for all the plugs and wires replaced.
I have two questions on this situation:
1. I never saw a code for the cylinder misfire. The only code I saw was for the o2 sensor that I mentioned above. Does it sound reasonable to claim that it's the plug/cable, or is he just throwing parts at it rather than properly diagnosing it?
2. I had a major tune-up, which included all new plugs and wires, 29k miles ago (18 months ago...) as I mentioned. My first inclination was to say that I should just have them change the plug and wire on the mis-firing cylinder. The dealer refuses to do this, saying he really would recommend doing all six "for my safety". He won't give me a better answer. Is there any sound reason that I shouldn't replace just the one?
Also, I think cylinder 6 is on the front of the engine, right? How hard is it to reach this plug if I wanted to do it myself?
Posted May 4, 2007 at 10:37 am
The rear (or downstream) O2 sensor really does not affect engine performance. That's the job of the upstream O2 sensor. The second sensor monitors the air after the converter to see that it is cleaner than what went into the converter.
Posted May 4, 2007 at 10:58 am
Posted May 4, 2007 at 11:06 am
valiant - yeah, i understand the difference between the two sensors. i'm worried that if it's really a problem with the cylinder and not the sensor, i could blow the cat if i keep driving -- if the sensor is functioning, it's telling me that the cat is not burning enough pollutants. that's why i wanted to get a sense of whether it's possible to see an o2 code and no cylinder misfire code if it really is a cylinder misfire.
bob - thanks, do you have any more details on that recall? i have access to alldata, and i did a quick search. there's a lot of TSBs, and i can't figure out which one you might be thinking of.
thanks again, all. and if anyone has thoughts on my original two questions, i'd appreciate it!
Posted May 4, 2007 at 02:35 pm
Posted May 5, 2007 at 07:32 pm
Posted May 5, 2007 at 07:46 pm
Take it back to the dealer and let them cover it under the 8/80.