Bassballplaya27

Now i knew something was deathly ill with my car when it sputters at a 1/4 throttle (about 1100 RPMs), but the funny thing is it only does it when its warmed up. Tight as can be when its cold, after 30 min of driving it acts up. Sooo i drive down to Shucks and use their OBD1 Tester Thing and he prints my report out, all is well. IT Says i have Code 42- Electronic Spark Timing circuit grounded, I ask the guy what it means and hes like i dunno and im like is it the opti-spark and hes like the spark plugs you mean .... By now im frustrated and leave.

So i need a little advice what does an- Electronic Spark Timing circuit grounded mean???? Is this the Opti or what??? Please Direct me to a generel source of error.... Oh ya its a 94 Z28.

Injuneer

DTC 42 = Ignition control circuit grounded. This is one of the most difficult codes to crack. It can reflect insufficient voltage in the white wire from the PCM to pin B on the igntion control module (ICM), it can be set if the high and low resolution pulses from the Opti are shorted to each other, or for opens in the ignition coil circuit, etc.

There is a very good diagnostic chart in the shop manual, that will step you through the logic tree for identifying the problem. A quick check would be to look at the Opti harness connector for corrosion on the terminals. Heat soak on the ICM might also be the culprit, and Shoebox's tech pages have a cure for that.

If you don't have access to the shop manual, I could fax you the pages.

Bassballplaya27

i dont need the manual, but thank you very much.