Dickinson County Comanche

I’m not getting any voltage out of the O2 at all. The truck seems to run more lean than rich. I have a potentially good extra one laying around here so I’ll swap it in and see if that changes anything.

So how does the O2 sensor get voltage back then? From the heater relay?

As for poking through the board, I tested every one of the resistors I could and they all checked out fine in terms of ohms. None seemed to be blown out or bad.

Pin 35 is supposed to have 5V out at all times, correct? I have no voltage to pin 35 nor any continuity between any of the power or ground pins

Took the computer out and probed from all power source pins to the O2 pin and haven’t gotten any ohms. Would this be a bad computer? Nothing looks burnt out or broken so I’m not entirely sure what it would be.

Switched out known good relays from my 89. No change.

O2 heater is getting 12v at the sensor. Unless something with the relay is bad, I’ll have to swap them around and see.

Checked voltage at the ECU. Nothing.

Found out I’m not getting any voltage from the ECU to the O2 sensor. Wire checked out ok and the computer contacts looked good when I removed them so it might be a bad computer. I’ll have to research more before biting the bullet on a new computer though.

The diaphragm on the EGR is totaled. I have an extra EGR solenoid to place in to see if it’s working or not

Yes, but the ignition doesn’t blip out like before, so it’s not ignition. My guess is vaccum leaks screwing with the map sensor or maybe that bad EGR valve

I should have clarified better, it idles fine, just when you try to give it gas at idle-~1750 it runs like crap. If the ISA is the little stepper-motor thing that pushes the throttle plate open, it does function correctly.

It actually revs again! The CPS mustn’t been positioned correctly so after a quicky adjustment it actually revs again. Absolutely no power at idle-~1750 or so but after that it picks up and goes. Any ideas as to why it might do that? I know the EGR valve is no good so I’ll have to fix it eventually. I also lost a tire on my test drive. Pour one out for the poor Walmart cheapo specials FullSizeRender.MOV

I definitely think the CPS is mounted incorrectly now. I found a picture (after searching for one forever) of a XJ/MJ A904 and the CPS mounts on two spacers that I don’t have. The picture of the trans/transfer case is how mine is set up

My 89’ had a similar oil-pressure problem like this and it ended up being a worn out oil pump. I’d definitely check your sensors first though, just to be safe

Yep. I’ve never seen a 2.5 with an auto except for this one. Cleaning it didn’t help, but I’m still sure it’s something to do with the CPS. I checked the CPS on my 89’ and it came back perfectly within spec so I almost wonder if maybe the CPS isn’t bad or positioned incorrectly. I’ll have to check in the morning and see

It doesn’t seem to be that rusty but I’ll still probably just go ahead and give it a clean to be on the safe side

Unless both of my multimeters are bad, yes

AC. I tried DC too with no avail.

And when I say “nothing” I mean no voltage at all. It will still run with it reading 0 though

I actually just tried to probe the CPS for the correct voltage and I got nothing. Could it be that the flywheel got a little bit rusty due to sitting out exposed when there was no transmission on it?

It’s something to do with ignition. It runs just as bad with the air intake on as it does when it’s off. I appreciate the help though.

I’ve checked every connection I can and they all seem ok. Which sensors should I try first?

I just cleaned the main block ground to no avail. All of the grounds check out ok as well and they seem to be getting proper voltage (~12.01V or so)

The whole fuel system has been gone through. I have verified already that it is not something to do with the fuel system as it doesn’t rev even with me bottle feeding it gas down the TB. It has to be spark-related somehow as it is hit-or-miss when it revs up.