Stalling after fillup/warm start problems

'99 Grand Prix GT, 48,000 miles.
Dealer, several shops and many Internet resources have given me many solutions as to what might be wrong, but no one knows for sure. I can't
find a shop even willing to troubleshoot this one. This has been happening for almost a year. Any suggestions are appreciated:
My problems:
- Car shakes slightly at idle when engine is warm. - Car sometimes gives off strong gas odor when starting when engine is cold. - Car starts and stalls or cranks, shakes and won't start after filling up gas tank when engine is warm. Sometimes restarts within next couple of attempts if I push the gas pedal down. Sometimes I have to wait about 20 minutes, then the car starts (this is what happened to me a few times after filling up). It'll crank but the entire car shakes and pressing down on the gas doesn't do anything in this circumstance. - On a few occasions the car stalled without filling up and it was after I had been driving for a while, shut the car off and then tried to restart it within a short period of time. The car then will not start again for about 20 minutes. I can "almost" get the car to stall after shutting it off and then restarting it after it has been driven a while. The car will shake and then recover itself but still remain a little bit shaky. - Car does NOT stall after filling up gas tank when engine is cold. If car has been off for many hours and I start it and drive the quick under-a-mile or so just to get gas and not allow the car to get very warmed up, I have no problem. - Service Engine Soon light has never come on when problems occur.
Fuel pump and fuel filter changed. New gas cap. New spark plugs and wires (routine maintenance). MotorVac carbon cleaning service performed (which fixed another problem where my gas pedal was hard to press down, presumably from a carboned up throttle body). No gas leaks. No trouble codes set.
Somebody...help... Shops will suggest problems but express uncertainty how to fix it and say live with it. It's driving me nuts. Main suggested problem is the Evap system. Anyone ever have similar problems and if so how'd you fix it?
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My Astro Van did something similar, turned out to be a defective coolant temperature sensor. The van didn't shake but ran rough sometimes until it finally failed. The sensor was telling the computer it was cold and flooding the engine when it was hot (choke). Just an idea..

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Michael wrote:

Possible/probable leaking intake manifold or burned out intake manifold, depending on engine.
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Look at the vacuum hose to the fuel press regulator see if it is wet inside with fuel, also with the line off turn the key on no start see if any fuel is evident on the line attaching port on the regulator, if so the engine is loading up when shut off hence the problem. Or an injector could be leaking down, harder to find this though.

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I find it hard to believe you can't find a shop or a dealer willing to troubleshoot this problem. I can more easily believe you can't find one that will offer up a quick answer to a difficult problem.
--

-Mike-
snipped-for-privacy@alltel.net
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