1G Intermittant lean condition turned into all the time lean

[randomdsmphrase]

Please help guys and I hope this is posted in the right place. If not please let me know. First time poster here with a 1991, Turbo, Awd. Mods are in my profile. So problem started awhile ago with intermittent, hot start, lean condition where the car would chug and want to die after long drive, shut down and restart. Just on hot starts. Cold starts were good. Didn't bother me too much. Then one day I noticed headlights werent working, then auto seat belts stopped working, then battery started having a draw. After that I literally unplugged everything from car on a draw test and could not find the drain for the life of me. :-( Then comes the nail in the coffin. One morning I realised I had left battery hooked up over night and it drew down to dead (thats how bad the drain was). So I hook up jump box to it and I reversed polarity like an idiot!! Battery dead instantly and i pulled cables instantly. Throw a new battery in and car starts and runs but runs crazy lean at all times now except for on start up when in open loop (correct me if I'm wrong there)? Ran a intake leak test and found nothing there so I know it's electrical or mechanical. I just don't know where to start. Im overwhelmed by all the electrical problems. What I'm thinking is that whatever was causing it to run lean intermittently before has now gave out completely because of the jump box episode. I've checked fuses, ran intake/boost leak tests, etc. Just trying to figure a good starting point or if anyone else has experienced this same thing. Thanks in advance for any help.

 

[19gsx91]

That's a crazy long post you've got there.. Also why did you post this twice? My immediate thought on it going lean on a 1g is your o2 sensor being bad, as for the electrical draw, have you verified grounds, or more importantly that non of your power cables have rubbed through?

 

[randomdsmphrase]

That's a crazy long post you've got there.. Also why did you post this twice? My immediate thought on it going lean on a 1g is your o2 sensor being bad, as for the electrical draw, have you verified grounds, or more importantly that non of your power cables have rubbed through?

Sorry for the long post. Like I said at first it was a couple minor problems and then it got out of control. Sorry didn't mean to post twice. My phone is a piece of junk. Lol. I have checked wiring everywhere. Even put in a new rewire kit for the fuel pump because previous owner did a pretty messy job of it. One more thing to add is that when the headlights, power seat belts and battery draw started to occur in noticed that the fuel pump started priming on its own with key on. It use to prime after I bumped the starter once. I don't know if that makes sense.

 

[randomdsmphrase]

That's a crazy long post you've got there.. Also why did you post this twice? My immediate thought on it going lean on a 1g is your o2 sensor being bad, as for the electrical draw, have you verified grounds, or more importantly that non of your power cables have rubbed through?

Plus I did find on what circuit draw was but I could not find the draw on the circuit. It was the mpi circuit that had the draw.

 

[19gsx91]

Then you need to trace all of the wiring from the MPI fuse backwards. There's nothing wrong with having a lot to say, just break it up into sections so it's easier to read. A lot of people are gonna look at the post go ohh... nope don't have time to try to read that paragraph.

I still recommend you swap front o2 sensors or at least check voltage.

 

[randomdsmphrase]

Then you need to trace all of the wiring from the MPI fuse backwards. There's nothing wrong with having a lot to say, just break it up into sections so it's easier to read. A lot of people are gonna look at the post go ohh... nope don't have time to try to read that paragraph.

I still recommend you swap front o2 sensors or at least check voltage.

I will check the mpi circuit again and I'll check the 02. I did take it for a quick drive earlier where it was warmed up but not running terribly lean and noticed that my 02 was reading rich on deceleration and lean on acceleration. Almost like the 02 was reading backwards. Like I said earlier it runs great till it warms up.

 

[19gsx91]

When it's cold it is in open loop mode, where the computer just automatically assumes everything is okay and does not check anything.

When it warms up it enters closed loop and primarily relies on the front o2 sensor for feedback on what the AFR is supposed to be.. it should oscilate up and down, if you had ECMlink you could monitor it and see for sure that it's working, without it my guess is if you haven't changed it since you've owned the car.. It's time.

 

[randomdsmphrase]

When it's cold it is in open loop mode, where the computer just automatically assumes everything is okay and does not check anything.

When it warms up it enters closed loop and primarily relies on the front o2 sensor for feedback on what the AFR is supposed to be.. it should oscilate up and down, if you had ECMlink you could monitor it and see for sure that it's working, without it my guess is if you haven't changed it since you've owned the car.. It's time.

You're exactly right. Do you know the best way to bench test the 02? If it turns out to be bad Is there a certain 02 to buy with the aem harness or will any one work? Does an 02 failure on these cars normally start as an intermittent problem as I described or could it go eit her way? Thanks for the help by the way!

 

[19gsx91]

It can generally go either way. Just replace it with something that will plug right in. bosch sensors work just fine. They're normally around 50 bucks. If you have an advance auto parts near you use online code TRT30 and you'll get 30% off orders over $50

 

[randomdsmphrase]

It can generally go either way. Just replace it with something that will plug right in. bosch sensors work just fine. They're normally around 50 bucks. If you have an advance auto parts near you use online code TRT30 and you'll get 30% off orders over $50

Will do. Thanks again man. I'll keep you updated on what I find.