I just got done putting a new wiring harness in my 87 Iroc LT1 swap. It was a custom harness and I went ahead and put a 97 Harness in. OBD1 (95 computer)

Now everything seems great. Started first shot, idled great drove great through all rpms. BUT I got on the highway and when doing 80-90 KM it was bucking (slightly barely feel but could feel through the ga pedal and the speedo and twitching when it was happening.)

I didnt have time to scan as I was taking my friend home, im sure she wouldnt wanna drive around trying to scan at 12am lol.
When I scanned during first start up the only new code I got was MALF 42 EST GROUND (but i relised my tach was taped into the wrong wire) I meant to tap into the neg of the coild (green on 97 and taped into the ICM White wire (white is neg coil on 95) SO I switched that so Im sure the code is gone.

Also I have the light blue TCC lockup wire wired from the PCM to the brake switch (same as it was before.)

Is there a way to test lockup?

Thanks Jay

 

I still have the MALF 42 EST ground error, I drove it to work this morning and still have that error and the convertor is locking according to data master, driving along it locks unlocks on the screen (0 unlocked(green light) 1 locked (yellow light) When on the brakes it always is unlocked.

Any Ideas?

It’s a 97 harness 95 computer 94 tranny. Had no issues until I switched the harness.

Jay

 

A 95 PCM is expecting to recieve a signal from the PWM (pulse with modulator) from the tranny to control lockup. A 94 tranny does not have a PWM. This may be your problem. Of course there's a host of other things too. O2's bad, a short in a wiring harness wire, etc. etc.