Stayed up for most of the night trying to troubleshoot... Just finished my swap into my '90, but I'm having a high idle issue at the moment, my rpm stays up around 2100 rpm. Originally I had the wrong MAF hooked up (my engine is a 96 and the MAF was from a 99) and it was causing 2CELs (MAF and IAT codes) and the truck to run so rich it burned my eyes and smoked almost as bad as a diesel.
However, it idled right around 900-1000, so I swapped out the new style MAF for the old style. Now, the truck runs cleaner and I have no codes but I can not get the idle down. I have started the truck without the throttle cable attached, cleaned and regasketed the IAC (and it works from the sound of it) got a new thermostat when I installed the motor, and checked for side to side play in the throttle shaft... Nada.

I will say the only thin I haven't done is check for vacuum leaks because I am out of carb cleaner and my propane torch is empty.. Just wanted to see if anyone had any other ideas for me to check.

Oh, if someone could post a pic of how the PRE 98 MAF plug is pinned out that would be great, I have my EWD to look at but I'm not sure I have it right. Thanks everyone!

 

So little bit of an update, i tore everthing back apart, ohm'd the MAF (within spec), tested for continuity between the MAF and ECM (good connection). Then i took the truck for a drive since i had not driven it for more than a few miles. About 4 miles in, the truck started throwing a p0125 code for the ECT system and i was a bit lost at that point since it had not thrown a code like that yet.

So, one of my buddies has a scanner that shows live data and we hooked it it, everything looked normal (MAF is reading, temp is 183*, TPS is sweeping) until you got to B1S1 o2 sensor... It wasnt showing a thing. we checked for continuity from the senor to ECM, good there. I had bought a universal fit sensor that was listed for the truck on RA and welded a bung in so we thought i might have gotten wires mixed somewhere, but our wiring seemed to check out, so i'm left with what i assume to be a bad sensor and a dilemma now-

The Upstream o2 sensor for the 5vze uses a flange type bung in the original vehicle, i currently have a screw in style bung in the upstream exhaust, but since i reused the 3vze exhaust the downstream sensor still has the flange fitting... Can i put the o2 sensor there temporarily until i can find another bung? Will the Cat skew the reading for the o2 sensor?

OR

Can i use the '01+ sensor from a newer 5vze that is a screw in type with the '96 harness? (I guess i'm really asking if someone can check their EWD for me and see how the b1s1 o2 sensor is pinned out on the connector, i would imagine the sensor itself and how the ECM reads it is the same.

Once again, thanks guys.

 

you cannot use the newer style sensor as its actually a a/f ratio sensor. The pre 99 are oxygen sensors.

 

Thanks for the info Vital, didnt figure i would get that lucky. lol went ahead and ordered the one meant for the harness last night, gonna try to cut the flange and move it pre cat.