i have a 2002 mercury grand marquis... it has 132000 miles.... when car starts it turns off like 5 seconds later. but if i keep holding gas it stays on with out problem but as soon as i release gas it shuts off.. anybody know what could be wrong.

 

idle air control is probably clogged up. it is located on the side of the throttle body. Just hose it out with some carb cleaner and get all the carbon build-up out of it and you should be fine after that. Take the opportunity to clean out the throttle body too while you're at it. It's probably nice and black behind the flap. Read the directions on the side of the carb/throttle body cleaner can and just follow those for the cleaning part. if you take the throttle body and idle air control off, you'll need to get new gaskets for when you put it back together (which isn't a bad idea and saves having to crank the car repeatedly to clear out the excess cleaner cause it'll all be in the catch pan under your parts instead of the engine).

 

fuel pump maybe...

 

if he keeps his foot in it, it will keep running. This shows the fuel delivery system is fine.