DoctorZ

I have an '87 Carrera that's been modified with 964 cams and (I think) a lighter mass flywheel. After about a year of ownership I noticed that when I blipped the throttle or when the car was coasting to a stop, the revs would drop to around 250 and then slowly climb back to 750-1000. One mechanic replaced the idle-speed control valve but this didn't fix the problem. I had another mechanic look at the car and he replaced the fuel pressure regulator. This didn't fix the problem either. Now, the car won't idle at all. It shudders and shakes at 250 rpm and just dies. Does anyone have any idea what the problem could be? Thanks

Crimson Nape Racing

the idle is adjustable. I don't remember exactly where since it has been several years, but that would be a good place to start. There is also an speed sensor located on the driver's side at/near the flywheel that went bad on my 84 - the car ran fine, but wouldn't idle - then it started intermitently (sp?) missing at higher speeds.

DoctorZ

Thanks. I will have my mechanic check both items you mentioned. I forgot to mention that the car has a high-performance chip. In addition to improving performance, I presume it should be able to handle the lower-mass flywheel. Do you think it might be acting flaky?

Steve W

Try raising the base idle speed, and having the idle mixture adjusted. However, oftentimes, cams with a lightweight flywheel need chip modifications to prevent subidle dipping such as you are experiencing. A standard performance chip without these mods will only exacerbate the situation.

DoctorZ

Thanks. All I know about the chip that's in there now is that it's from Autothority. Perhaps they could help me if I called them.