O2 Sensor

[project 92z]

Recently acquired another 92 Z34. The wiring harness has a single wire male plug taped in with the EGR valve wiring. It doent seem to have a female location to be plugged into within reach. A friend of mine suggested that it was the lead for the O2 sensor. After some digging around down there, I didn't find a O2 sensor- in fact, the bung for the O2 sensor seemed to have been sealed off. The car is running very rich and we're thinking that's why. My question is do you guys agree and if so is there a way to counter that either with a tune or chip?

[Schurkey]

NO O2 sensor?

The computer is going ape-shit trying to figure out which way is up. There is NO way around not having an O2 sensor that will leave performance and/or economy intact. The computer can be forced to run in open-loop all the time, but it's going to object.

A prehistoric one-wire O2 sensor is less than $20 for a quality unit, if you look around.

I'd want a scan tool on that computer, and detailed inspection of the rest of the vehicle to see why some moron thought removing the O2 sensor was a great idea.
First Guess: Broke the old one off in the manifold, said "screw it" and promptly sold the vehicle when it couldn't be made to run right
Second Guess: Failed wire harness or failed computer, engine didn't run right with the old O2 sensor, either.

"Unseal" the hole in the exhaust manifold, go from there.

[project 92z]

Thanks. I was afraid of that. Getting to that manifold location is gonna be a b!÷@h. May have to pull the motor, right? Can it be relocated further down steam?

[Schurkey]

DON'T pull the engine.

Get underneath. The sensor can be accessed from below. On my '93, I cut the exhaust pipe ahead of the converter, removed the bolts at the manifold, and had nearly unlimited clearance. Put the pipe back together with a band-clamp. Simple, easy...but I could have simply removed the rubber hangers and not cut the pipe if I'd been thinking more clearly.

Or pull the intake manifold top off, which gives you room to access the O2 sensor from above. When you're in it that far, pull the intake manifold lower out. Re-gasket the intake manifold, clean out the EGR passages, gasket the oil pump drive, and flush the coolant.

You could weld a bung into the exhaust pipe between intake manifold and converter, close to the manifold. The farther away from the manifold you are, the slower the O2 responds.

"I" would be looking for a replacement exhaust manifold IF (big IF) you can't get the O2 sensor out of the original. Of course, once you remove the exhaust manifold, a machine shop can probably repair the O2 sensor bung.