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Title says it all. I pull the code religiously when the engine isn't up to temp. My o2 sensors are quality and less than a year old. my air/fuel guage reads normally after warm-up, but during it reads dead rich.

Denso are the factory sensors. Anything else your taking a chance. MX6 says Walkers work well, many have used Bosch. Hows your VAF?

I've tried a lot of o2 sensors, at least three brands since I installed my a/f ratio guage. I don't remember the brand of the last ones, but I remember thinking that I've never seen a readout as "crisp" as what I've got now on my guage.

Anywho, about the VAF, I'm not really sure, I've read some conflicting stuff as far as what kind of ohm readings you should get on 'em. And some theories about deadspots due to prolonged readings at certain speeds. I know I've got a few dead spots, but I've never found a junkyard VAF that didn't have the same dead spots, so I'm not convinced that's a problem yet.

Too bad you don't have a spare you could swap out. I like having spare parts, just need an ECU and I've got one of everything. You could try cleaning the VAF resistence wire with contact cleaner. Just don't blast away at it, spray in easy bursts. Google it there's lots of info on vaf cleaning. How's your CAT, could it possibly be a little plugged? Anyway cheers.

Ok, just tested out the VAF today. I think it may be suspect. Any gurus out there wana comment?
Got the readings off of F2-152 in the 1992 Manual

All readings @ roughly 20 deg.C

E2 - Vs = anywhere from 1100 ohms to 620 ohms closed (should be 20-600), 260 ohms to 340 ohms open (should be 20-1000).

E2 - Vc = 283 ohms, absolutely no fluctuation from close to open, stays rock solid on this reading (should be 200-400 closed-open, that mean this one should change?).

E2 - THA = 2700 ohms, that should be fine since it was probably a little colder than 20.

Spray the element/resistor and gently clean it with contact cleaner (no lubricant) then try it again. Usually as you shut down the engine a pulse of higher voltage is sent to the resistor and that cleans it but they have been know to stay dirty. There is a post here on cleaning these,,,,I think I may of posted it. lol

I'll give it a whirl. I'm figuring the element/resistor you're refering to is inside the moving part. I can't see any wires anywhere, the back of that part seems to be the only spot where there might be access. It's too bad you can't disassemble these things.

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Ok, I just drenched the piss out of the VAF with contact cleaner, the E2 - Vs readings were quite a bit lower, so I think it helped with that. But the E2 to Vc is still 283 ohms solid. Can anyone with a little spare time on their hands confirm if that's correct or should it change resistance between open and closed.

The two terminals are the 2nd and the 4th, with the measuring core on the left, or the right, 2nd and 4th no matter wich way you look at it, pretty much idiot-proof.