I am having a problem with my 1986 IROC-Z Z-28 with the TPI injection system. My car runs absolutely great until it warms up and goes into closed loop operation.....My car has thrown code 42 (EST), and 23 (manifold air temperature)....but it only throws the codes once in a while whenever i am screwing with it.....the symptoms is that is starts backfiring and power loss almost like it is missing......and it runs real rich guessing from the smell of the exhaust.....if anyone could tell me where to start and go from on my car to make the damn computer not screw up the way my car runs!!!!!
Thanks

 

My car is doing that same thing right now. Im going with an ignition module and some tests Vader mentioned. Im getting smoke and thunder at 200 RPM after its warmed up. Im not getting a code...wish I was. However i did have a code 42 many moons ago. It turned out to be a bad ground right at the ESC control module on the firewall I think that wire was Brown. Car would idle fine but as soon as I brought throttle up the code would set. Also I had the temp sender wire on my knock sensor. Stupid ***'s made the conections the same. Anyway my knock sensor obviously wasint functioning. So maybe your knock sensor went for a crap.

 

By the way my trouble was 2000RPM not 200. Just wanted to add for the sake of trouble shooting, that its a single wire to the knock sensor and its white. Youll see it on the ESC harness.

 

Thanks Edge i will have to try that when i get a chance!!!
Thanks again!

 

When you say 'screwing with it', do you mean removing electrical connections via the ECM with the battery hooked up?

I remember when I ran a TPI, it would go into 'limp home' mode the second I 'jiggled' a connection!