1991 Mitsubishi Eclipse 91 Eclipse- RPM to 0 when warm &

Electrical problem
1991 Mitsubishi Eclipse 4 cyl Front Wheel Drive Manual 190K miles

After starting and running the RPMs start going dirctly to 0, as if the accelerometer was disconnected. Sometimes the car continued. Sometimes I had to keep cranking the car till it came back on. Later I had to wait till the car cooled and it would start again and go a short distance.

My mechanic says that he didn't find anything wrong. He recommended it may be a heat sensor in the distributor that's shutting off my engine. He also said it could be the computer. He did not give me any codes. He said it was a 50-50 chance it could be the dist or comp.

Now, the problem has gotten progressively worse over time. It takes less and less time for the same stalling problem to happen.

Is the problem a heat sensor that's gone awry? Can I do it on the cheap and by-pass this sensor? How can I be sure which part is the problem?