Replaced coils, housing, boots, plugs, crankcase position sensor, etc, and still not working. We have a '93 Grand Am, 2.3L SOHC, that is not passing emissions testing. We replaced the O2 sensor, per the error code on the diagnostic machine. Still had problems. We asked a neighbor who is a mechanic what the problem could be and he suggested replacing the coils, which we did. Still had the problem. We took it to the dealer who diagnosed it as bad coils/coil housing/boots. We replaced the coils again as well as the housing and boots, plus did an entire tune-up. It ran fine for about 30 minutes and then the problem came back. We took it in again to a State inspector who again diagnosed the coils. Again, we replaced the coils. Same problem. The inspector ran a full compression test and everything came back good. The motor itself is fully in spec. The inspector called his supervisor who said that maybe it was the crankcase position sensor, which we just replaced and still have the same problem. Supposedly there isn't a strong enough current being sent to the ignition coils. Does anyone know what in the world could be the problem. We have spent way too much time and money on this car only to be told the same things over and over. I'm definitely pulling my hair out and would appreciate any help I can get. Thanks!
One simple thing to rule out is low compression. Performa a compression test to ensure that is not the issue.
August, 23, 2012 AT 3:10 AM
Thank you very much for your response. We did get a compression test done today and all came back great. The thing that was a bit odd was that when the inspector put the Vantage Pro Scanner to the different wires of the harness that connects to the ICM, there was some spiking of the signals. For example, the scanner should show the 4 cylinders signals on the scanner (it looked like an EKG test) with 2 bars in the shape of a rectangle for the 1st cylinder and 1 bar each in the shape of a rectangle for the other 3 cylinders. Instead ours was looking like a really pointy mountain (2 on the 1st and 1 on each of the others). Also, sometimes the voltage on the same harness only showed 6 volts instead of the 12. Also there was some mention of a ground issue but it ended up working correctly after he found another ground. I am at a total loss, as was this master mechanic inspector. Any ideas?
August, 23, 2012 AT 3:12 AM
Replace the spark plug housing on the top cover, common failure.