1997 Chevy Astro 6 cyl All Wheel Drive Automatic 122000 miles
After the car heats up and after a left turn the engine runs very rough. I put a scope on the coil wire with a trigger from number 1. At idle the spark time is about 30 msec. After failure, there are intermittent extra spark firing between the 30 msec pulses. If I shut off the engine and re-start it is normal. Distributor, wires, coil, ECM have all been changed. At the time of the miss fire the communication to the Snap On scanner becomes erratic. My question is, is there a singular point in the ground circuit that would make the ECM "think" it is getting an extra pulse from the crank sensor. When these extra spark pulses fire you can hear a ping in the engine. Previous to this, the fuel pump and filter have been replaced and the rail pressure is 55# at idle, increases as the engine revs and returns to 55#. This has been beating me up for over 2 months of troubleshooting.
have the same problem?
Tuesday, August 31st, 2010 AT 8:14 AM