w8ng4u

peeps, help a brotha out!! Let me give you the run down on my issues. I have an 87 GXL. I'm having some erratic issues with my trailing ignitor/tach. When I first try to start the engine the tach works but jumps like it keeps losing signal. Once the engine is started the tach stops working along with the ignitor and trailing coils. I've already replaced the ignitor and coils, but issue still continues. I tested the crank position sensor and coils per my service manual specs. I was thinking it was maybe a ground because when just one set of coils is firing the engine, if I create any current draw (windows, lights) it wants to make the engine die. Here's what I would like to find out if nobody has any other ideas.

1. Location of all ground points that could affect the ignition system.
2. If there is a way to monitor the signal that is sent from the control unit to the trailing ignitor.
3. When testing the resistance in the wiring from the ignitor to the control unit, what an acceptable reading would be.
4. Is it possible to take a jumper from the primary coils to the trailing coils and just have them fire together.
5. If they make an aftermarket igntion system. (who, where, how much)

Thanks

Icemark

what is the voltage on the factory voltmeter when you are having this problem.

It should be at 14+ volts.

w8ng4u

it usually sticks right around 12 volts. I tested the alt and it's still putting out 14 volts to the battery.

NZConvertible

The main ground point for the entire EFI sysytem (including the ECU) is a bolt on top of the rear rotor housing. The coils are grounded directly to the body through their mounting brackets.

To get any useful info you need an oscilloscope or an engine diagnostic monitor like mechanics often have.

Should be almost zero.

Nope.

You don't need one and it wouldn't fix the problem anyway. The stock system is capable of supporting highly modded Turbos.

Icemark

Then you have some serious power issues... how did you test the alt???

w8ng4u

NZConvertible, thanks for all your help. it turned out to be the main ground strap you mentioned on the back rotor housing. it was cut halfway through. thanks again for your input.

NZConvertible

Glad to hear you got it sorted.

It's amazing how important that ground is. I had my UIM off the other weekend, and I removed and cleaned up that ground. Somehow that damn bolt has worked loose (probably wasn't tightened properly), and I now have the nastiest 3800rpm stumble you could imagine. It's impossible to get a spanner onto it because of the intercooler bracket, so the UIM has to come off again this weekend. I am so kicking myself for doing something so dumb!