That's not what I meant.
The security switch is only one part of the setup. Foremost is that the sensor plate position defines the mixture for every operating condition. This can be understand as a sliding window. The higher the window the leaner the mixture and vice versa. When engine stalls after throttle release the mixture may lean too much ti keep the engine alive.
How many turns do you need to fully close (cw) the idle screw? (Remember old setting and reset it afterwards).

Thomas

The engine does not stall after throttle release. It is like a switch shutting off with the engine at part throttle and under load. It does not sputter, mis-fire, or buck. The engine simply stops running. Immediately turning the key off and back to the START position instantly re-starts the engine and it will run and drive normally for 20 to 60 minutes before it happens again.

Dying ignition coil...lend another one and go for a test ride...this advice has been given earlier too. Did you crosschecked it already?

Not to highjack the thread by i have the same thing going on with my 930. It is the same symptoms.

Those can be eliminated by simply inserting jumper wires around the relay socket.
It doesn't get any easier and less costly than that!

That's not typically representative of a fuel problem on a CIS engine, i.e. the fuel pressure will not immediately go to a level shutting-off the injectors,
with the exception of FA (fuel accumulator) failure or major leak. A pressure loss will result in some cranking time, e.g. a few seconds, to rebuild the pressure.

They have ignition problems too!

I personally would rule out the ignition first. So check all ignition & plug wires, rotor and cap, ignition coil (I wrote that earlier), CDI box and the green wire from the distributor to the CDI box.

When engine goes out, does the tachometer directly falls to zero too? I would record a video with a tiny action cam mounted on top of the steering wheel column with sound to hear and see what exactly happens... The professional would wire a ignition timing light seeable outside the engine compartment to monitor if the spark goes away before engine stalls or not...

Did you wiggled the green wire when engine idles? What happens? Green wire is the timing signal for the dizzy to the CDI box and there's literally almost no electrical power there...only inductive pickupas on all 911 SCs (up to 1977 all CDIs were triggered with points!). Be aware about the high voltages coming out of the CDI to the spark plugs, it's potentially mortal!!

Thomas

CDI box is sent off for testing. To correct my earlier post, the short section of the green wire at the distributor is new but the rest of the wire to the CDI is not. The wire had been replaced with the longer 928 part at some point prior to my purchase. I clipped the old pickup off and added an AMP connector when I installed the new, correct short wire/pickup. The old wire section may be the problem. While the coil is a possibility I think it is less likely because the car immediately restarts. If the car needed to cool down before restart then the coil would be more suspect in my mind.

Thanks.

Bob Ashlock tested the CDI and found it to be functioning 100%, even when stressed (heat, etc.) I have a new fuel pump relay socket and green wire on the way to (hopefully) rule out those things as the culprit. I'll be checking the power wiring to the CDI over the holiday to eliminate that as an issue.

More to come.

Replaced the fuel pump relay socket with a new part from user Timmy2. Here is what some alarm system "installer" did to the previous one when they installed an aftermarket alarm for the previous owner.
http://forums.pelicanparts.com/uploa...1732921910.jpg
To answer Thomas' question about tach needle behavior when the car dies, the needle does not drop immediately to zero. Rather, it slowly drops as the car slows. This leads me to believe the issue is NOT related to the CDI or green wire. I plan to take the car for a drive tomorrow and see if the stall returns. More to come.

Well, with the holidays and December/January weather behind me I finally got the 911 out today for a beautiful Sunday drive in the +65F sunshine to see if replacing the FP relay socket addressed the problem. Car ran fine on the 90 minute journey to our lunch destination. We sat for about an hour having lunch and the car fired right up when we were ready to leave. About 45 minutes into the return trip the car again lost power. After pulling off the road I immediately cycled the key and it fired right up. We drove on and about 20 minutes later it died again. This time I was on a fairly straight stretch and moving about 60MPH so instead of pulling off and re-starting I simply switched the key off and immediately back to the RUN position while still rolling along at around 50MPH. Power returned instantly and everything drove normally. I had to do this once more during the remaining drive home. I did notice that after the engine quit before I cycled the key the oil pressure and oil temp gauge needles stayed at the last position . This says to me that those gauges lost power. I'm starting to suspect the 15 bus contact in the ignition switch or the wiring at the switch is the culprit. That part of the switch feeds power to the speed limiter relay, fuel pump relay, and CDI.

Then you didn't lose #15 power, or the temp needle would have dropped - it needs 12V & the oil temp takes awhile to cool resulting in a needle movement.
Typically, having to cycle the ignition switch after an engine shutdown, indicates a SCR latchup problem in the CDI.

Hello all,

Just a little follow-up to (hopefully) close out this thread. I believe the root cause of my problem was an intermittent fault in the alternator.

I had the original externally regulated alternator rebuild by a reputable local shop about 8 or 9 months ago. It had been performing flawlessly. However, in the last couple of months I noticed that intermittently the GEN light would come on, then go out again. After a few different drives it became more frequent. I was able to verify with a voltmeter after a couple of jaunts that indeed, the alternator had stopped charging. However, when starting the car dead cold the alternator would start charging every time only to intermittently stop charging later as indicated by the dash light. I pulled the alternator and took it back to the re-builder for diagnosis. They found that the shaft end opposite the pulley had just enough wear that occasionally, the rotor would just "kiss' the stator, shorting the field and killing the charging. They built up the rotor shaft and machined it to spec. I installed the repaired alternator and my original CDI box and went for another +150 mile drive today. Everything performed flawlessly. I need to put some more miles on it before I plant the victory flag but I think this is resolved. Big thanks to Bob Ashlock for the loaner CDI box to help get this figured out.

Good to hear you found the problem.

Thanks so much for posting the final solution. It will surely help someone down the road.

Regards

Remember, if an alternator intermittently dies, but the engine will crank and immediately start, the engine shutoff is NOT an alternator problem,
nor a loss of the 12V battery power! An engine will run with a dead alternator!