1997 Buick Century • 48,000 miles

No start when operating temp, sometimes.
Have had a random no start condition four times in two years. Weather was not hot, between 50 and 75 deg. F.
After a 50 +/- mile trip vehicle rested only a few minutes and had to be moved. Tried to start, engine cranked but missed and backfired through intake and barley ran even with throttle to floor, similar to an out of time condition. Opened hood to look around to notice intake manifold hot as a pistol. (This may have been due to backfire and combustion taking place in manifold.)
I asked a mechanic friend about it and said "It's got to be the ECM. This was replaced and it happened again. Now what? A sensor affected by heat?
April 2, 2013.

When it doesn't start, have you checked for spark and fuel to the engine?

My guess Is it had both as it sputtered and backfired through the intake and as I stated before seemed out of (ignition) time. I had nothing to work with at that point. For the record, when the engine cooled for a few hours it started and ran flawlessly. The fuel pump motor was audible during "no start".
I will be purchasing a FI pressure tester and a new digital 7 function multimeter, (my old meter is analog) and keep them in the trunk.
This malfunction is totally random and only occurs when at operating temp, so is the reason I believe it may be a sensor affected by heat when engine is shut off with static ambient air in engine compartment.
Is there any case history on this condition?
The concern is I've turned this car over to my Daughter and need it to be dependable.

Apr 2, 2013.