I feel your pain but unfortunately have no suggestions. Following hoping for a solution.
Johan

I would check all of your grounds:

Battery neg to chassis
Behind fuel filter
Intake runner
i think 2 others in the frunk
Transmission ground strap

Only happening at operating temps sound like heat expansion - could also be ecu internals related?

What is the syndrome called when a car won't restart while warm?
Owner has to let it cool down and then it starts fine?
Heat soak? What is that?

Sounds like you are overheating a component in the DME. I'd send the ECU to Ingo

My personal list of what I would suspect when a 3.2 suddenly dies when hot but runs fine otherwise:
- DME relay
- Speed and reference sensors
- Head temp sensor esp. if original 2 wire type.
- DME
Since you've replaced the 1st 3, I'd suspect the DME at this point. Swap DME's with a friend. the idle speed changed over the model years but for testing purposes, you should be fine.

Note: If you have a black ignition coil, keep it unless you know it is bad. Replacing it with a newer silver coil "while you're in there" is a downgrade in reliability in my opinion.

Just an update - and an opportunity to thank all those who have chimed in with experiential suggestions - I am in midst of cleaning all ground connections while waiting for new plug wires...If the problem persists, its time for a DME check up...Who is Ingo, where can I find him? Sounds like he's the place to go...Thanks again you all, immensely...

ischmitz on the forum, he helped me a ton with a DME issue and a very nice guy.

Subject matter expert Ingo Schmitz

I'll PM him for you, Scott

Here you go:



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I had a mysterious engine misfire, and was stumped. I finally looked at the coil itself. It was oozing black goo. The real pain is no one really sells a new perfect replacement coil for the 3.2. The Porsche dealer will sell you a new coil in a Porsche box that is a total waste of money, Bosch branded coil made in Brazil. Those are oven NFG right from the box. The aftermarket coils are all the wrong voltages.

I finally located a OEM Bosch black coil from a junkyard. It has been perfect. Check your plug wires, especially the coil wire, and the coil.

And get a solid state DME relay sold by on of the members of the board.

Update: Cleaned ALL grounds, changed out plug wires with new set. Initial reaction was positive, car felt zippy and tight. Upon reaching temp, she burped a bit just to warn me she was about to cut out...And she did. I sat for 30 seconds, fired her up and she got me back around the corner where I started - and died upon applying the parking brake. I know all about the silver coil from brazil, er I mean Bosch...TWICE before! I am not ruling out heat soak of the coil, which occurred before with my 930...Not knowing squat about the DME I will get it ready to send to Ingo...
As soon as I figure how to post pics, I have some "where does this wire go" questions for the group. Thanks again all.

I would also double check the resistance of the CHT sensor you fitted - appreciate its new but Bosch (?) quality hasn’t been the best for a while, I had a brand new one changed out within 50-100 miles a few years ago.

In fact I believe there is a way of jumping the CHT, to remove it from the ECU circuit, purely for testing.

See ChrisBennet’s post from another thread:

http://forums.pelicanparts.com/porsche-911-technical-forum/213741-engine-cuts-out.html

Just because you replaced the Crank Positions Sensors with new doesn't mean that a new part is not faulty. A new part can and will be faulty out of the box...

There are a couple of solder joints in the DME that you could check for yourself if you can solder. I would check the fuse and fuse connections to the fuel pump. In my case there was a bad connection to the hot wire to the fuel pump that was intermittent when run more than 30 minutes.

I could not fix the problem until it failed completely. It's hard to diagnose a problem if it is working when you are testing it.

I traced a lot of wires, checked harness continuity, cleaned a lot of grounds and tested and retested. I did send the DME out, and it was worth it just to eliminate that as the problem. I had a bad AFM on another car. It would cut out, but only at specific RPMs where the resistor strip was worn out.

It was worth it to me to work on it myself. How is a mechanic going to diagnose it any better if it doesn't fail while he is working on it ?

But less likely, and the symptom would most likely be total failure, does not run. It seems like something is getting hot and failing under hot load.

I had this happen with crank sensors. Failed when hot, then cooled then OK. Replaced with new Bosch (now made in the Peoples' Republic of China) - failed soon after. Finally got a good one in there...

Sure sounds like cracking solder joints on the DME circuit board.

One other thing I’ve seen is a tachometer that would heat up and short out the primary ignition circuit. Try unplugging the tach next time it dies, just go rule it out.

This probably isn't your issue, but in the interest of providing more options than none...I had a similar issue, and it turned out to be the ignition module overheating due to a lack of heat sink. This was on a 3.6, though:

http://forums.pelicanparts.com/porsche-911-technical-forum/966521-whats-smell-wait-why-isnt-my-car-running.html

It looks like the 3.2 ignition module is built into the heat sink, but maybe the internal connection isn't great anymore, or the engine bay is getting too hot now...I dunno.

86 3.2 here...had similar issues a few years back. Wasn't DME relay...wasn't grounds...wasn't wires or the coil. It turned out to be a bad solder joint in the DME that allowed it to run fine untill the unit heated/expanded. I took out and had to look twice before I found the crack. I re-flowed the solder and all has been good for years now.

Ok this is an easy one. Only because it’s happened to me with customer cars a few times.’ You have done all of the right things so far but I am seeing this more often. Open the rear deck. Look to the drivers side where the three sensors on the rail plug into the main harness. As the main harness makes a 90* turn under the outer shielding is where you will probably find cracking on the crank sensor wiring. Most but not all, I have found all three cracked. This problem will only get worse till it won’t run at all. That’s when they usually get towed in.