1997 Buick Riviera starting/stalling problem

HI Everyone,

I have a 1997 Buick Riviera with the supercharged

3.8 engine in it. I'm having one heck of a problem. The car has been to my local mechanic and two buick dealers and they can't figure it out. I'm close to just starting to replace parts. Here's some symtoms:

1. If I drive the car to operating temp (200) and let the car sit for a bit (like if I go out to eat) if the car temp drops down between the

6th and 7th tick on the temp guage (which appears to be 160 degrees) it will crank but not start. This doesnt happen all the time, maybe 1 or 2 out of ten times.

1. When I am at a red light the car may stall or attempt to stall but catch itself. Again this is not all the time so it's hard to reproduce.

2. When I am driving if I hit the gas hard the car will sometimes stall. Doesn't happen all the time. Appears to happen when the car downshifts. I have reporduced it twice, two days in a row to where if the car is between the 6th and 7th tick on the temp guage and I floor it it stalls out. It takes about 10 minutes of cranking to get it started. It does sound like it fires one or two cylinders every once and a while

1. Sometimes I'll be coasting down a hill, not hitting the gas and it'll just turn off.

2. It's throwing a crank shaft position sensor problem code.

I've changed the sparkplugs and wires and the ignition coil. The crank shaft posisiton sensor was checked by all three places and they say it's ok. Wiring harnesses were checked. My local mechanic had the car for about 5 months total time and can't figure it out.

So the key points here is that these problems occur 90% of the time when the car is between the 6th and 7th tick on the temp guage. Once it cools down to the 5th tick it starts fine. When I turn the key to unlock I can hear the fuel pump prime.

Any ideas?

Sam