[danielt]

911 engine experts,
Got a new challenge for you. While driving to work the other morning, the car began to stumble and run extremely rough while cruising at 3000rpm. It would not hold an idle and would die instantly. After leaning out the fuel mixture for >30%, I was able to get the car to run, but idle was now at 2200rpm (normally 800rpm) and still extremely rich. The car has no power and seems to get weaker with more throttle. I limped the car back home and pulled the plugs. All are carbon black. After putting the plugs back in and restarting cold, it would idle at ~1200rpm with manifold vacuum at only 5-6". Normal vacuum at idle is 12-13". I originally suspected that the vacuum line for the fuel pressure regulators snapped, causing both the vacuum leak and the overly rich condition. That checked out clean. At this point, I have not found an obvious vacuum leak after checking all the joints from the heads to the throttle body. I have checked the fuel return line and it is not blocked so the fuel pressure should be controlling properly.

Current guesses:
1. One or both of the cams has slipped and is off. I would expect this to screw up the vacuum, but would it make it rich, too?
2. It is demon posessed and will require a priest to get it running right again.

Any direction and help is extremely appreciated.

Current condition of the car:
Big bore 3.2L
cams reground to 964 profile
Intake from an 1989 Carrera
Electronic fuel injection from SDS-EFI.

no issues like this for the first 10,000 miles on the rebuild.

Thanks,
Daniel