Engine racing and power loss followed by stall and non-start

[bomberoKev]

Hi- About a year ago, my wife's 1985 911 Carrera (US version, nothing modified on it) developed a problem that started showing up in the first few days after it hadn't been driven for a while (it is her daily driver, so generally gets plenty of use except when we are out of town). After about twenty minutes of driving, the engine would start racing at idle, and under acceleration would lose power, stutter and feel it was going to stall. Sometimes this would stop after a bit, a couple of times the car would eventually stall and refuse to start (it would crank, but not start.) After being left for a couple of hours, the car would start up and drive fine. She took the car to the local Porsche mechanic, who was unable to replicate the problem.

After a recent period in which the car hadn't been driven for a few days, the racing/power loss showed up after about a half hour of driving. It never actually stalled, but when I stopped the car and restarted it cranked but did not start and would not start for the rest of the day. (It was a hot day, about 85 degrees out, if that is useful) The next day, it started and could be driven home, but the racing/power loss problem returned instantly and is now so severe I hesitate to drive it.

Any thoughts on what this might be and how to go about diagnosing it or suggested resources? I am a newbie mechanic but have the long term long-term goal of learning the car and being able to work on it myself, so would like to make an initial investigation myself. In addition, when the car goes to our well-regarded but overworked Porsche specialist, it tends to disappear for a very expensive month or two, depriving my wife of her car and (IMHO) giving the car additional problems from non-use. Thus, while this is likely going to be beyond me to fix, I'd like to get as far down the road as I can, in order to learn something. I'd also like to at least be able to talk intelligently with our mechanic and perhaps cut the amount of time he has it. Many thanks.