Originally Posted by heavymetals
A bad O2 sensor won't do anything except trip lean codes.
Yes! Although it will also cause rich, high voltage, low voltage, circuit performance, and cross count DTC's as well.
Originally Posted by 1BADCTS
It can cause a misfire if it's throwing off the a/f enough to cause premature or no fire. And it makes sense that it would then be random, not consistently one cylinder.
Unlikely. I have seen Long Term fuel trims at -100 and it still did not cause a miss. A vacuum leak is usually the only thing that will cause a lean misfire unless the fuel injector data is way off in the tune.
Originally Posted by St Louis SHO
I see them all the time, just more on the 5.3 & 6.0l truck engines. The o2 shorts internally, and causes it to be fat as ****, kills the plugs, then you can figure it out from there.
Shorted - an abbreviated term to indicate that an electrical circuit is traveling along an unintended path.
Shorts to what? Voltage? Ground? The median 02 sensor voltage is .450v, if it stays over or under this baseline value for too long it will set a crosscount DTC (this sets if the 02 sens. voltage does not cross this .450 threshold a specified number of times within a set duration) and will be disregarded. The 02 sensor itself generates electricity based upon the difference in oxygen content between the atmosphere and the exhaust.
The PCM averages the AFR by crossing the .450v threshold which translates into rich/lean. The sensors can get poisoned, read lazy (shooting way over like .820v then to .270v rather than staying closer to the .450 baseline), or just be dead...although most times it is indicative of another problem that has manifested (ie., vacuum leak, leaking injector, worn valve seals/guides, etc).
It would take a lot of fuel to cause a miss (enough to smell and know there was a problem), and I wouldn't think there would be that much adjustability in the fuel trims alone to allow that much fueling unless the tune had been altered. I guess if there was a rich condition for long enough (caused by a leaking injector, regulator, etc) the sensor could get poisoned and read lean over time, inducing the higher fuel trims in addition to the unmetered fuel, but that's what I would be looking for.
Maybe you're speaking in vague generalized terms when you say "shorted", although it is not actually shorted. Many people say something is "shorted" to mean its fucked up when it's not really "shorted" to anything. It really bothers the **** out of me when people describe something as "shorted" when its actually open. It's a peeve of mine.
Originally Posted by 4door-6speed
I'm having an issue like this too.
I was at Gingerman a week ago Sat. Had the random misfire code followed by a bank 1 lean code. Reset the codes and saw the bank 1 lean code come back on Sunday. Then again on the ride home. Reset again and the bank 1 lean code came on again last week. Going for new plugs this weekend. What is the best way to test the o2 sensor? Or should I just change it?
There are different types of "miss fire's", they manifest themselves under different conditions and feel different. An ignition miss will be much more pronounced under a heavy load than that of a lean miss...something you have to get a feel for over time.
I posted to a thread a while back about diagnosing a miss and what to look for...I'll try to find that and link it here.
Edit: Here it is....Low RPM Misfire/Hesitation Issue