Sorry for the post, im a newb. I did a search and can't find anything. I was wondering what the front o2 sensors (before the cats) should be running at. I was looking at them and they were jumping from 16mv to like 800mv at idle. Is this normal??

 

I think so. When idling, and well tuned, they will jump up and down in a semi wave pattern. Im NOT positive, so hopefully some others will come in and correct me if im wrong.

Also, dont they need to be at 890-900mv?

 

During normal driving, the sensors are going to fluxuate (sp?) a lot to try and keep the engine around 14.7 A/F ratio.
But during WOT, they will settle down and this is where you should be seeing something between 890-910mv roughly.

 

^^^ correct, they should form a what looks like a sine wave ... they constantly switch high low high low ... as for the max... never really paid attention to that... so long as they are switching quickly and your ltrims aren't crazy then there's nothing to worry about

at WOT you can use them to a very limited extent to see what your fueling looks like... higher the number the richer... unfortuanetly there's no good way to correlate these values to a real AFR (need a wideband for that)

 

hmm. my car is a making me very angry right now. maybe if i drive it off a cliff and say it was stolen i can get some of my money back...

 

I feel bad saying this, but I can't tell you how many times I've contemplated doing this to my car.

 

Normal; the front O2 sensor voltages are supposed to switch like that; when they don't switch or when they switch too slow, PCM throws one or more DTC's.

At WOT, PE is invoked, so AFR is richer than at PT, so O2 voltages will read richer (> 700 or 800 mV) and flat without switching while at WOT (or while in PE).

 

Remember to jump out before hand, otherwise theyll never believe you.

 

Better have a good alibi too...something that puts you miles away from the scene of the crime.