dfwcowboy57

I have a 96' v8 5.0 232,000 miles, When I go up hill it sounds like there is a rattle in the engine & i feel air being blown into the cab even with the a/c or heater off. When the a/c is on it stops blowing thru the vents & i can feel air being blown under the dash onto the floorboard. Just wondering what is going on & if I need to get something fixed, thanks in advance for any info.

sylver91

Most likely a vacuum leak. Commonly its because of the the small white line on the passenger side under the hood near the firewall.

Warlockk

The rattling noise sounds like you are describing detonation ( knock and ping). Could be cause by a vacuum leak or it could be carbon, bad gas or timing/ignition problem causing low vacuum that would cause the vent to change to default. Start by checking for codes, then check your timing. Then look for vacuum leaks.