Gary

Folks,

Just posting for a friend - he has just acquired an '91 964 cab and it stalls frequently when coming to a stop at traffic lights etc. On my 951, this can be caused by bad TPS, lack of (or badly adjusted) throttle body CO adjustment screw or vacuum leak somewhere.

On the 964, I have absolutely no idea where to start with the problem

I understand from searching that there is no idle adjustment and no TPS although sometimes, people use the CO adjustment to adjust idle. Is this CO adjustment basically an air bypass valve (as on the watercooled Porsches)?

Any advice/comment on where the problem could lie?

Does anyone have a link to a picture of the CO adjustment screw? I guess it's on the throttle body somewhere(?).

Thanks and Best Regards,

Gary
Switzerland.
'86 951
'01 325Xi
'04 XC90

Andy Roe

Gary,

Has his car got a light weight flywheel installed? This can be a sysmpton of the standard ECU not being able to keep up with the quicker reduction in revs when you lift off the throttle. This problem is often enhanced on cars with Air Con.

Regards,

Andy

Gary

Thanks for the (really quick) response Andy.

No, it's a fully stock car; however, it does have aircon and he does use it due to the warm weather at the moment and the fact that there is a small problem with the roof mechanism such that if he opened it, it would be really difficult for him to close again...

Gary.

springer3

The engine controls on the 964 are complicated, but they work unbelievably well. I would not ever consider jacking around on the CO screw attempting to fix a different problem. Check for threads on cleaning the ISV (idle stabilization valve), and the belt driving the secondary distributor. What is the idle speed when it does idle?

If all else fails, get the DME fault codes read (threads available on that as well). I think you will only make a mess if you try making adjustments to correct for an unrelated component failure.

Wachuko

Start by replacing the DME Relay and then follow the suggestions from springer3. If some one overfilled the oil you could have contamination in the ISV.

deep_purple

Gary,

This is a very common problem, with many possible causes.

Here are some related threads:

Thread 1

Thread 2

Thread 3

Good luck!
ST

BaysideC4

This happens to me every time my battery is disconnected. After my mechanic adjusts the idle with the hammer, everything works perfectly. I hope its that simple for you.

Gary

Could just be a terminology issue here but what's a "hammer"

Gary.

Andy Roe

Gary,

The "Hammer" is the Bosch diagnostic tool the your mechanic would plug into the car to re-set the ECU & diagnose any faults.

Andy

deep_purple

I don't know if this is the correct one, but I think it looks like this:

PRAV

Hi Gary,

Happened to me on 2 occasions. Both were due to a condition where the car runs extremely rich under idle conditions. The remedy was a recalibration of the airflowmeter - the mechanic explained to me that they are very sensitive and sometimes go out of calibration

joey bagadonuts

My car stalls with the change of seasons (an abrupt occurence here in the Midwest). I simply reset the engine managment system or chip. You simply unplug the ground for 20 minutes, then reattach, start and let idle for a few minutes, then take it out for a spirited run. The chip relearns the variables and driving conditions and adapts the engine's peformance accordingly.

I do this a couple times a year and it eliminates the stalling for me.

sxton04

I purchased my 964 in June of 2012. Ran very well but eventually started stalling, randomly, when stopping at intersections.

Replaced fuel filter, cleaned out idle adjustment valve, and added fuel injection cleaner to the fuel. Nothing seemed to help.

Took it into a new shop, Highline Autosport in Blue Springs, Missouri. Turns out the "mass air-flow" meter/sensor was fouled-up. Had it replaced and also changed the air filter with AEM, "DryFlow" filter.

Part was $450.00, after returning the core. Total parts and labor was $699.00.

Runs like a dream!

Vandit

Your 964 has a MAF? Is it aftermarket or off a 993? What supporting mods does it have to make it work?

964s have an air flow meter aka flapper box.

Opo

I have the same problem and this is what the dealer order for it