Stray Ignition

[ralendrum]

I will try toi keep this as short as I can. After tuning up my 1990 C4 the ABS and PDAS warning light were on (as well as the main"!" light. When I test drove it the CEL also came on. All of a sudden the lights started flashing on and off. The CEL light flashed once and the engine cut out when it did. I went home and parked it for a while then read up on it. My computer scan said that the ABS / PDA Relay was faulty. I also got a code that said the ABS module was bad. The more I read the more likely it seemed to be Ignition Interfeirance.

After carrying out all of the tests I could on the ABS system I started looking towards the ignition. This is where it got interesting. I unplugged the harness plug at the rear Ignition Controller (Ignitor). When I did this the car ran exactly the same, lights on and engine cutting in and out (getting nervous). I plugged the rear plug in and unplugged the front one. The lights went out and the engine nevr missed a beat. I even test drove the car with the rear plug on the front ignitor/coil. It worked fine. So the question is what could make it act up. I know the signal wire from the ECU is a shielded wire.

Any advice would be a great help.

Bob

[magcuda]

Usually this is caused by spark arcing from the boot to the engine

But you swapped the plugs, so check for acing from the rear coil

[wvicary]

I would guess the ignition control module is failing. Also verify the operation of both dist. rotors as the drive belt can break causing the secondary rotor to stall and a cylinder misfire which can damage the engine if not sorted.

[ralendrum]

I figured the problem out. I thought that the wire from the ignitor to the coil was seperate so that when you plugged in to the ignitor you were also plugging into the coil mounted above it. Turns out the ignitor has no external wiring and has nothing to do with the coil mounted above it. The wire (Green to the forward coil) actually comes out of the plug. This means that the ignitor has nothing to do with the problem so no matter which one you plug into you are still running off the coil that mates with the plug/harness.

Bob