Hey guys. I just bought a 1986 Grand National. The car is completely stock except for a air cleaner and had a hypertech chip in it. I brought the car home on a trailer, it was idling high when I test drove it but seemed to drive ok. The previous owner had replaced the MAF, TPS, ICM, ECM, Coil pack, Cam sensor, 1 injector on number 3, plug wires, and spliced the injector harness.
I started doing the spring cleaning to the car, changed the fluids, plugs, cleaned the MAF, replaced the O2 sensor and was adjusting the IAC and TPS. I have a Scanmaster and a Scan tool for the car. The TPS was set at 1.2 and IAC was at 175. So I adjusted down the TPS to .46 and the check engine light came on sometime during all of this. Code was 42. I adjusted the IAC down to 46 counts and the TPS sensor down to .44 and the cars idles a lot better but pops if you rev the engine up. Reset the ECM and am still getting a code 42. So I replaced the Hypertech chip with a stock chip, wiped the codes and I am still getting a code 42. I found a few articles that had flow charts on testing for a code 42 all of my tests pointed to a bad ICM, so I replaced the ICM with a new one and am still getting a code 42. Plug wires are on the right posts on the coil pack. I hate to throw parts at this car but I'm kind of at a loss here. Was hoping someone could give me some insight on what to do next or what to test. I haven't drove the car since I brought it home 3 weeks ago....
I started doing the spring cleaning to the car, changed the fluids, plugs, cleaned the MAF, replaced the O2 sensor and was adjusting the IAC and TPS. I have a Scanmaster and a Scan tool for the car. The TPS was set at 1.2 and IAC was at 175. So I adjusted down the TPS to .46 and the check engine light came on sometime during all of this. Code was 42. I adjusted the IAC down to 46 counts and the TPS sensor down to .44 and the cars idles a lot better but pops if you rev the engine up. Reset the ECM and am still getting a code 42. So I replaced the Hypertech chip with a stock chip, wiped the codes and I am still getting a code 42. I found a few articles that had flow charts on testing for a code 42 all of my tests pointed to a bad ICM, so I replaced the ICM with a new one and am still getting a code 42. Plug wires are on the right posts on the coil pack. I hate to throw parts at this car but I'm kind of at a loss here. Was hoping someone could give me some insight on what to do next or what to test. I haven't drove the car since I brought it home 3 weeks ago....
