After the car has been sitting for a while, I'll go and try to start it and it will start fine and Idle at 750 RPM's, soon as I put the car in reverse and give it gas it seems that the pedal will just go flat with no response, the car will shut off.

Soon as I crank the car again the problem goes away and I'm able to drive. I went to Volvo and got new wires, cap, rotor, air filter, fuel filter, thinking that maybe the car just needs a tune-up. But this didn’t cure the problem, also the car only got 41,000 miles on it.

I check fuel pressure at the rail and pressure seems fine, I check IAC valve and cleaned it with some carb cleaner. Alternator is making some funny noises, but it's putting out 14.4 Volts and on the crank the battery drops about 1.5 volts. I never checked the TPS sensor, and I never checked for ECM codes because I don’t know how to check for codes. Is it possible to read ECM codes like GM cars by using a paper clip and jumping the terminals?

So I took it to a local import guy and let it over night, the next morning he told me that the problem goes away so quick that he can’t get a good reading, he recommended that I take it to the dealer. (The dealer is too expensive and in the past having received no results with past problems, just a large bill!

What do you think could be the problem?

Thanks