My 964C2 has a warmed over engine with Cup cams and remap , lightweight flywheel , de-cat exhaust . Recentlly serviced , new plugs and tappets set.

On cold start up , the car always fired up at say 2500 rpm then dropped right back say under 1000 rpm , then picked up and oscillated 1500 to 700 , steadying out after a couple of minutes to a 1100-800 'hunt'.

In recent months it has occasionally stalled on that first drop back.

Starting from warm it never stalled.

I took it out on a recent trackday , had to keep some revs on whenever I had to stop at traffic lights etc when cold on the journey out , no problems at first on track , then it stalled when reversing back into pit garage. After that it seemed susceptible to stalling when warm on the return journey.

Checking it out a few days later after a cold start it would not keep running without I gave it some throttle ,for 5 minutes or so to move oil temp needle off stop but as soon as had to take foot off throttle -to apply brakes- it stalled .

What are the likely causes ??

 

Sounds like the O2 sensor John. Had exactly those issues and a new sensor cured the problem immediately Rob

 

Agree, had this on my 964 RS and now my 993 has the same issue. Annoying but relatively easy and cheap fix.

 

Thanks ras and barty , will put this on the list of possible causes - will be going into the specialist in 10 days time ( Unit11) and no doubt they will run the hammer ( Bosch ! ) over it . The big headache was how do I get it over there without being towed or transported as the lightweight battery only good for a limited number of restarts.

However - good news - boxsey popped round to have a look and suggested disconnecting the Hall sensor at the distributor.....tried this and it fired up and then settled down into a lumpy idle ( normal ) without intervention , and drove round the block without stalling , so at least will be able to get it to Unit11 in confidence.