Ford Repair: 5.0 stumbling, vacuum leak, time bob

Question
"I have a 94 full size Bronco with a 5.0 with 85k on the motor. It runs out very strong, just recently when I am stopped at a light with the truck in drive and holding the brake on the engine stumbles, idles down and some times stalls. Putting in back park it starts back up with no problem. It does not do this all the time, only after running for 30 minutes or more. Can you help?

Thank You for your time

Bob  

Answer
You may have a vacuum leak or bad idle control valve. This engine had problems with leaks at the throttle body gasket, and the plenum gasket where it joins the intake manifold. The IAC can be checked by disconnecting it with the engine idling, the idle should drop or stall with this disconnected. If the engine doesn't stall then I would suspect a large vacuum leak or a stuck IAC.

Have you checked for codes? That could lead to the direction of the repair needed.