Ignition Leakage

[ralendrum]

So the problem started after I did some work on my car. I have a 1990 C4 that I recarpetted, replaced the B&B exhaust with stock, set valves and replaced plugs. When I went to take it out for test drive the ABS and PDAS warning lights came on and stayed on. I did the usual and checked fluid level, charging etc. I have the Durametric program and checked for fault codes and came up with the ABS Relay and / main module both faulty. I carried out all of the voltage and continuity tests. Evrything checked OK.

Since I could not find an issue I test drove the car and the CEL came on. Again the car ran fine but I noticed that the lights started to flash in no particular order or for no reason. Whenever the CEL lights flashes off and on the engine stumbles (loses spark). I had read that the "Christmas Tree" effect could be caused by stray high tension voltage.

My next check was to reset all of the spark plug and Distributor boots. No Change. I removed the plug from the forward spark control unit (ignitor) and started the car. Voila problem solved. I plugged it back in and removed the rear plug. Same problem. At this point I assumed that the forward coil was probably starting to break down. Wrong.

I unplugged the ignitors again and plugged the fron plug into the rear ignitor. Same problem. I plugged the rear plug into the front ignitor and the car runs fine with no lights on. SOOOo

I assume that the problem is in the plug or specific wiring from the harness to the plug. I see in the wiring schematic that the signal wire from the ECU is shielded and the shielding is negatively grounded.

Has anyone run into this before? Have you cut into the harness? Is there any chance the problem could be elsewhere (not likely since it seems so specific to the forward plug)

Any advice would be greatly appreciated.

Thanks
Bob

[ralendrum]

Well after extensive trouble shooting I resolved the issue. I won't bore you with the details but in the end I pulled the bottom plug wires and plugs. I tested the wires and rechecked the plugs. All were OK. I put everything back together and the problem was gone. Now the only warning light that comes on is the low washer fluid. I will have to lookinto that one day.

The moral of the story is look for the easiest things first. I still find it hard to believe a miss installed plug/wire could cause things like the ABS / PDAS and the engine to completely quit. I have since driven the car 200 Km without a hiccup.

Bob