300CE M104 CIS (1992) hot running woes

[robertb1958]

OK I have two of these frustrating cars, both with similar problems.

The '92 (with 95K MI) starts readily when cold, with maybe a little off idle stumble for a sec, then runs well at all RPMs and throttle positions while still cool, and much of the time when normally warm. In fact, the engine seems super smooth and strong when it is running right.

Sometimes, though, it gets to running very rough when warm. It has stranded me twice by shutting off then not starting back up. Now I am reluctant to drive it anywhere.

When this happens (its not every drive), the poor running gets progressively worse over about a 5 min period, it is not all of a sudden. Seems like 1 or 2 cylinders start skipping first. Also, it seems that if you can get above idle/low throttle input/low RPMs into high throttle/RPMs, the problem clears while operating there. Tough to do at a stop light, putting in neutral and revving is not enough. Once, it about died on me, but luckily I was able to get to an open road, and then the issue(s) cleared after some driving?

If it matters, the tachometer operation seems normal during the fits. On my 944T, the tach quits when the DME relay is acting up.

Sure would appreciate a checklist.