Viprklr

iTrader: (5)

If I hold the throttle above say 1500 rpm I have an intermittent quitting of the engine. It just dies and immediately starts back up on it's own.
Happened to me while driving. I can also re-create the RANDOM death in the garage.
Symptoms:
Car dies
Tach drops
Engine light comes on
TCC unlocks

Car starts back up on it's own in less then a second and everything is fine. TCC tries to find itself. My assumption on this is open vs. closed loop.

The definition of a miss only extreme.

Testing results using a scope:
CKT 423 and CKT 424 both lose signal.
CKT 423 - white wire, pin C8 coming from ECM to spark control module.
CKT 424 - tan tan/blk wire, pin C7 coming from ECM to spark control module.
Wiggling/pushing/pulling wires at the ECM and module did not cause a repeatable occurence.
I've had the module tested and of course it tested fine.
This is not temperature related. Nor is it vibration related.

What do you guys think? Bad ECM, TCC, SCM? Something else?

The car is the 92 SD 350 730 ECM running S_AUJP_v3.

tony_cogliandro

iTrader: (3)

i think you have a short which is creating an intermittent failure.
it sounds all electrical.
just a guess but look at your distributor - sounds like something is moving around inside and giving you a short.
look for the little black marks.

Viprklr

iTrader: (5)

Pulled the dizzy. All looks well. It's even a new (1 year, 300 mile) dizzy. This problem just showed up last weekend on a little joyride.
I agree on it being electrical. Intermittent electrical problems are the bane of my existence.
I have a new 162 (most updated) ECM on the way. Figured i'm in for a dime........
What's another 100 bucks?
I just have some doubts about it being the issue.

Quick_Trans_Am

iTrader: (2)

I would check the pink ignition wire that goes in to your ignition coil for breakage. Also pull the 2 wire pigtail going from the coil to the ignition module and test those for continuity. Test them with the wires in different orientations (i.e. : flip-flop them around while you're doing a continuity check to see if there's breakage in the wire at a certain point).

A lot of times (more often than not from my experience) the module can test good even if it is faulty. Can you force the engine in to this condition when it is cold?

Viprklr

iTrader: (5)

New ECM didn't fix the problem.
However I did find that the pink 12v wire going into the coil was periodically shorting on my plenum dizzy cover.
This wire is apparently hot in run.
What could I have fried? The only thing I can see is either the coil or the ignition switch. Is there anything in the ignition switch that can fry or is that strictly mechanical?

Off to test the coil.

Viprklr

iTrader: (5)

So:

ECM is good
Ignition module is good
P/U coil is good
Ignition coil is good

hmm. I hate electrical gremlins.

Quick_Trans_Am

iTrader: (2)

The pink wire is what supplies the 12v to the coil. It becomes energized when the key is turned to the ON position. If it is shorting, it's not completing the circuit and therefore would cause an issue similar to what you've described.

Viprklr

iTrader: (5)

Yep.
Figured that out with the schematic.
It's running right now. I'm watching the voltage on that wire.
IF the engine has it's hiccup and I see it on the DVM, then i'll replace the ignition switch. If not, then I guess nothing was fried, just shorting.

Viprklr

iTrader: (5)

Can't duplicate now.
Must've just been a short.

Thanks for the help.

Quick_Trans_Am

iTrader: (2)

Glad you got it figured out. I hate tracking down electrical bugs, but at least it's an easy fix.

Viprklr

iTrader: (5)

I guess I spoke too soon.
I couldn't duplicate the symptom in my driveway. I did find that while driving it the symptom persists.
I guess now i'm waiting on the new ignition switch.
I'll go for another drive today with the volt meter hooked to the power wire. Gonna see if the power is intermittent to the coil.

tony_cogliandro

iTrader: (3)

the most common electrical problem is intermittent failure. so what you check out that looks ok only means it was ok when you checked it out.
only total failure would show up.
have you tried looking at the obd1 data as soon as it happens.
all you need is a paperclip and the ability to count blinking lights.
there are lots of postings here that show how.
i remember that i even posted a couple along with links to sites that showed the codes and that the usual problem is.
the obd will keep it in memory for a while only then it gets overwritten.
that is the only way to get past problems and will work for an intermittent fault that i know of.

Viprklr

iTrader: (5)

Yes.
No codes.
I was even datalogging when it happened for the first time.
Everything points to a complete ignition failure for a split second.
The output of the ECM to the ignition module dies. That tells me that either the ECM or wiring is faulty. Also that it's input signal is disappearing.
The failure of the input signal to the ECM is what i'm waiting to rectify now.

Romilin

Did you ever figure out this issue? Seems im after the same Gremlin now. The only difference is that the Check engine light occasionally blinks RAPIDLY like there is a short. But no codes saved.......

Viprklr

iTrader: (5)

Not yet.
I thought I was on to something with the ECM fuse/power under the hood. I've been looking at the schematics trying to find a common denominator.
Of course, after I stabbed the wire and hooked up a voltmeter....going for a drive.....the problem didn't show. Go figure.
Power coming out of the fusebox is fine.

Bottom line, I still don't trust it.