1991 2wd 3.0, with 3k miles on rebuilt motor. All stock.

My 3.0 is running really rich. While I don't need a smog check now, I had it checked and it's in the "gross polluter" realm. Exhaust smells like fuel.

All vacuum tubes checked. EGR working properly. Air injection working. O2 sensor working, although putting out the full 1 volt. No fault codes. Timing is correct. It idles fine.

What is the sequence of things to do to get this rich condition fixed? I'm reluctant to just start throwing parts at it (injectors, MAF, plugs, etc.). Is there anything short of hacking the ECU to lean it out a bit?

 

Perhaps the ecu is not not going into closed loop.
Have you tested the engines coolant temperature sensor.???

 

I can check the temp sensor. How would I know if it's not running in closed loop?

 

"How would I know if it's not running in closed loop"??
That's a good question and I don't know off hand what the FSM says about that.
I would expect that a fluctuating O2 sensor reading would give an indication of closed loop, but IDK for sure.
I do know that if the coolant temp sensor does not give the ecu the good word, closed loop will not occur.
I'm sure there are other parameters that must be satisfied as well, but that is the first place to look.
I have an old Snap-On MT2500 scanner with Toyota OBD-1 proprietary software that can tell me about open/closed loop, but that doesn't help you any.

 

I was checking the leads on the MAF, per the FSM. All combinations had the correct resistance. But...I noticed that the connector is missing a female lead. Can someone check theirs and tell me if this is wrong?



It's the connector to "E2" on the MAF.

 

That plug looks the same, with that one lead empty, on my 1992 4runner wreck.

 

Great. Thanks for the info.