SQLGuy

If pulling the fan fuses helped, and switching on the blower caused some hesitation, then your evidence seems to be pointing to electrical noise confusing LH, EZK, or both. Problem is that that could be caused by a bad ground for either of the boxes, or for pretty much any sensor that feeds them (EGO, MAF, Temp, etc, etc).

If you have a fairly similar reference car (late S4 or later, I think) an oscilloscope or a good DVM, like a Fluke 89IV, that will measure AC + DC (at the same time) could be used to compare values at LH and EZK signal, power, and ground pins relative to a known-good ground....

P.S. Nice car! My favorite color. If you want to trade, my GTS doesn't hesitate.... :-)

Lizard928

GP III under 14 pin connector for final stages measured .3 ohm resistance (off body) to final stages. Cleaned it and added solder to connection now zero resistance.

Lizard928

Interesting to note that the fan controller by the passenger seat has been opened up and it looks like a couple solder joints have been touched. But they all don't look great.

Lizard928

I cleaned GP III and still noticed the problem in the shop.
I also the reran all the solder connections in the fan controller module.
Hooked up the ST II, and took at for a drive. I couldn't reproduce the symptoms.

Needing to get Steve back to the shop and drive to test as sometimes cars just don't have the problem when I drive.

SQLGuy

Has MPIX (I think it's 9 - the one under the FPR) been checked/cleaned? This is where the LH gets a lot of its reference.

Leon Speed

Maybe you just mash the pedal all the time

Lizard928

The two ground points at the back V of the engine are fresh and clean when I replaced the engine management harness.
Meeting Steve in 10 min and will continue testing, but as of yet cleaning GP III and resoldering the fan controller seems to have cured it.

Fingers crossed!!!

Lizard928

Did a ton of driving/testing today. Could not reproduce symptoms.
I had Steve drive, still didn't happen.

He took the car back and phoned me a few hours later and said that it did actually happen again. ARGH!!!

Lizard928

I can't seem to get the pictures off my iPhone to load even via the app.
But on Steve's car the fan controller is missing 3 wires (comparing to my 87 with same pn on controller) out of the two plugs for the fan controller.

It appears to be missing the some of the percent wires. Would this make a difference?

GregBBRD

I'm having a tough time imagining a fan problem that would cause a 928 to mis-fire. The two systems seem like they are/should be fairly independant. It seems like you'd either have to be "robbing" voltage from the ignition system, sharing a really "poor" ground connection, or have a couple of wires that are "touching" each other, inside the loom.

Try running voltage directly to each coil, from a direct source (disconnect the original source) and see if the mis-fire goes away.

jcorenman

Could the missing wires be for the louver motor? That was all deleted for the GTS, and the motor is/was connected with three wires.

And +1 on what Greg said, good plan.

canuck0199@hotmail.com

Looks like my jump post has been modified.

How many wires are supposed to be attached to the post.
I have 4. 3 red and one black.

Thanks!

Rob Edwards

Here's my '93 GTS jump post. Stock, AFAIK:

canuck0199@hotmail.com

Thanks,

I have an extra black wire on mine, maybe for an amp.

Steve

Rob Edwards

That would be a weird place to pick up 12V for an amp, but who knows? Which direction does it go? Certainly worth tracing to see where it goes.