1986 911 3.2 stalls below 1500 rpms

[Amberjack]

Long time 911 owner (this car), new poster on the forum. Several years ago the car developed a stalling issue at low rpm's. Different mechanics have been unable to solve the issue. I'm hoping by going up on the board another 911 owner may recognize the symptoms and suggest a solution.

1986 Carrera 3.2 130,000 miles engine strong except for this problem

Car runs fine in warm, dry weather
Stalling issue seems to happen in cool or damp weather

On stalling days car starts harder and engine sounds different. I can't really describe it, it just sounds or feels different. I can get it out of the garage by keeping the rpms high but then the engine quits when rpms drop below 1500, with or without the clutch engaged--it just stops with maybe a couple pops. Once it stalls it becomes very hard to restart and will do so only after sitting for 15-30 minutes. But continues to quit below 1500 rpms. This is not a gradual thing, the engine runs OK above 1500 rpms but as soon as the rpms drop below that level it just stops.

New in the last 8 years:
flywheel-replaced about the time the issue began
distributor cap and plugs
head temp sensor
idle stabilizer valve
new fuel filter this summer and all fresh ethanol free gas

This must be a component involved with low speed rpm control that is sensitive to cool or damp weather but I'm not a mechanic and don't know enough about these cars to diagnose it.

[flightlead404]

This is a turbo forum you might have better luck in the regular 911 forum.

That said, once the car has warmed up does it run and idle ok below 1500 rpm? If so, then I'd suspect something in the warm up enrichment cycle, a temp sensor maybe or a leaky vacuum line that is blocked once the car reaches temp.

[Amberjack]

flightlead404-- Yes, it usually runs better once I can run it on the freeway for 10-15 miles to the office, then in the afternoon on the way home when it is a warmer time of day. We'll look at what you recommend.

I've moved this over to the regular 911 forum, thanks

[jpilcher]

Check intake manifold studs.. You may have an vacuum leak.
Had something similar, once warmed up ran fine. I retorqued studs issue gone.

[cabmandone]

If you haven't posted in the 911 Tech forum, I would. I have a 3.2 N/A. I'd start with the usual suspects being vacuum lines. You mention the flywheel being replaced. I'd think that if it was a speed/reference sensor gap issue it would show up regardless of temp. Solid advice about checking intake manifold bolt torque. Also check the boots on the intake for cracks. One other thing you might want to have someone check is the base idle mixture but I'd start by making sure the vacuum hoses are all in good condition and that the idle air control valve is functioning properly. I'd also check the idle switch, and WOT switch to make sure they're in good working order since each has input for the mixture. When cold does it smell really rich? Again, I'd start a new thread or see if the mods can move this to the 911 tech forum.

You want it here http://forums.pelicanparts.com/porsche-911-technical-forum/?daysprune=30

[911 Jay]

being this started right after or at the time of the flywheel replacement I'd be looking at the crankshaft sensors. These cars do goofy things if not gapped properly. Spec is 0.8mm. Need an old sensor to glue a shim to for proper setting or the transmission out so a feeler gauge can be installed. Best way to test these is with a lab scope. Resistance check and led light spelled out in the book tend to only work for truly dead sensors and not ones that are marginal.