I have 3 people working on this problem. One is a Mech with 25 years exp, another is an avid ECM Programmer, and myself.

First off, DON'T TELL ME TO REPLACE THE PICKUP COIL. Please. I've done this on this car and other cars. Usually the distributor will fail all together, as it did on this one.

Its an 86 GT 2.8 5 sp. Symptom is erratic spark when not bypassed. Car runs rough, stalls, especially bad at cold start. After keeping it running for 1-3 minutes, SES light will come on, and car will run perfectly besides the light. If from a cold start the EST is bypassed, it will idle smoothly and not stall, and properly reduce idle as engine warms up.

First thought was PU Coil, replaced and no longer ran. New distributor, runs, but has symptoms. Swapped ECM, ditto, 3 ecms later exact repeatable problem. Checked Dist module at ECM connector for proper switching of EST and Bypass, all ok, so wiring seems to be fine. New factory chip BCC APN, same problem, same problem in all 3 ECMs. Tried another distributor, same problem.

Mech. thinks it still has a bum distributor, Programmer thinks it might have a bad ground somewhere. My only other thought is a faulty reference wire, but it doesn't explain why it runs so well in bypass, since it needs the reference signal to fire the injectors.

Any thoughts? Trying to ready car for sale, and its excellent otherwise.

Chris

In bypass the ECM is still getting the reference signal but the ignition module is looped internally. The slight delay for the injectors is no big deal (it's actually 2 rotations late anyway).

I would suspect a ground.

Are you getting the Code 42 during the bypass? I would expect that if you are manually bypassing it.

How does it run in ALDL mode (A and B shorted?). That's a fixed 10 degrees. If it's still goofy, then you need to scope the reference line and again, grounds or a really leaky coil generating noise (which is what I suspect you have).

Very good! Thanks

I was assuming bypass was ALDL mode on this car. The instructions for setting the timing called for shorting the AB and there is no plug on the bypass line.

SO, yes it runs fine in ALDL mode. It sets the code with normal running. If i manage to keep it running from a stone cold start (which i can't always do), it will set after 1-3 minutes. I haven't clocked it to know exactly but its somewhere in there. It will do the same on a warm start, but I won't have to fuss with it to keep it running usually.

My note on the reference line, was that if it was dropping out due to a physical defect, the fuel should show signs of that in bypass as it would continue to have problems. But it appears to be totally spark problems.

I did find some leaky plug wires, even though they are fairly new. (the extra moisture from washing the car broght them out). But fixing them did not help the symptoms at all.

Thanks TK

42, spark timing... can be really annoying...

There are TWO grounds in the ignition that are absolutely critical.

One runs from the module to the ECM. That's the reference signal ground. Both the ref signal wire and this ground must be good.

The other is the main ground. With HEI that ground is made thru the ignition module mounting hardware. (DIS often has a second wire for it.)

If the module isn't well grounded to the block, then the power from charging the coil will rout to the ECM and everything else. This will cause weak spark and can fry the ECM.

If the Ref ground is bad then the ECM may have trouble reading the reference signal wire correctly. This will make timing go nuts if the ignition even fires.

Because the module grounds to the distributor, you need to make sure the distributor base isn't all corroded or something.

You might also want to try cleaning/replacing the screws that retain the module. In some cases the Module is built such that only the screw may be grounding it. Dirty screws or ones with anti corrosion coatings could keep the module from grounding.

You should also check the other grounds on the engine and battery.

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11-Sept-01, The day the world as we knew it ended.

Thanks, i'm gonna review the grounds and the coil.

bump cause well cause

quote Originally posted by FieroRookie: bump cause well cause

Gogswell Gogs?

Good advice above...

That would be my first test too. I would check the base timing. Mostly to eliminate this most basic setting from the equation and because it is easy to check.

The engine to frame and battery ground. This can cause the weird and unexplainable.

Jim