Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
I have a 1991 GMC Topkick, with a LP powered 6.0L engine. It is backfiring often when I press down the accelerator, it has a stumble, is sluggish, and the accelerator itself is spongy.
I've replaced the plugs, wires, cap, rotor, coil, and ICM.
It throws a code 42: "Electronic Spark Timing (EST) Circuit - Open or Shorted." When I disconnect the plug/wires going from the ICM to the ECM, it doesn't throw that code.
I am trying follow 'Scannerdanner's' instructions on isolating a wire to test for short to ground.
Does the ECM harness disconnect at the firewall? It looks like it does, but I am trying gently separate it, and want to make sure before more firmly pulling it apart.
Any other helpful suggestions on solving this problem are welcome.
Thanks!
