As the title says, when my engine is cold and i start it with my scanner plugged in, i watch the data, and one that catches my eye most, is where it says prom i.d., it keeps chaning numbers. Kind of like it's making up different i.d numbers. I have the 8902 prom installed in it. When it's in closed loop, it says 8902 like it should. Why would it not send the right i.d number to my scanner at all times? ALSO, when in open loop, my tps says all kinds of random voltages, my IAT sensor will go from -40 to normal temps, and my coolant temp sensor will do the same. When in closed loop though, things seem normal?? It's wierd. I really think my ecm is going out, car runs good, but doesnt run as it should when cold. It stumbles some, flucuates idle some. I do keep getting a ses light for code 32, but nothing i have done fixed it, new egr valve, temp switch, rconditioned harness. All my other sensors are new too, ALL OF THEM. top half of the engine was taken off, and I rebuilt the fuel rail, sent the injectors to cruzin performance, new o rings, gaskets, etc. So, should I put an ecm in it? HELP, lol. OBD 1 stinks!

 

Good possibility the ECM is going out. If this is the original setup for your '86 it has the '165 ECM. Which is know for this type of issue.

Try this: once the engine is up to temperature and in closed loop, tap on the ECM. If the engine stumbles or otherwise changes the ECM is bad. Classic for the '165.

RBob.