1993 Mercury Sable • 148,000 miles

My moms 1993 merc sable 148k is having a problem. It will start and idol but when put in park and drive it dies. The car will then turn over but not start. After it sets for an hour or so it does same thing. Oil pressure is good, battery is good, fuel pump and lines are good. Thoughts? Please help? I don't have the $$ to donate right now but I should could use some help. Midas can't figure out what the problem is.
December 28, 2012.

Your Idle Air Control Valve, IACV could be bad. It controls idle under engine load. Then you might have a problem with fuel pressure or a dirty filter or injectors. Replace the filter if applicalbe and get some BG44K. You will have to go to a car dealership parts counter to get it and it is $20 a bottle. There is not another fuel system cleaner that removes deepsoits and sludge the way it does though. Two bottles would be best.