Brandon's Z

I have what I am considering a weird one. I have recently purchased my second 1990 ZR-1 car 103.

This car was purchased at auction and I have been running the bugs out of it. It ran like SH## when I got it and now is running really well with one big issue that happen often.

Sometimes when driving the car it will have a single slight miss and then the Speedometer and AC both will quite. Then the SES light comes on and no secondary’s. The “Sys” Light also flashes indicating a code.

I ran codes the first time and got a 21,42,45,56,65. I put several miles on it while it would run great then go into the gremlin mode.

I cleared the codes (I have a OTC SPX Genies) and the car will still have this problem, but the ALDL will stops working and does not show any codes or even communicate.

When it is having this problem the scanner cannot communicate with the car at all.

Everything reads great then the gremlin appears and the scanner loses communication. I don’t have access (lost currently) my FSM. Any of the gurus around have any thoughts on why the ALDL would work intermittently like I have?

Demps

Sounds like possible ECM. I would swap it out (from your other ZR-1). Keep chip with appropriate car.

May also consider grounds on bell housing.

After this you're into DIS.

Ted

One other thing--are you sure battery is 100%?

Brandon's Z

Any chance anyone knows where I could get a ECM to test with or who is best to check/rebuild mine?