My cousin has a '96 F150 XL, that he just bought for a work truck, and the thing shifts into 2nd by itself while ideling down the road. As far as he knows no one has ever messed with the idle. Is this a common problem or is this truck just possesed? Please advise. ps other than this problem and a fuel pump on one of the tanks not working the trucks runs excellent and is in good physical shape. I think the motor is an inline 6.

 

what rpm does it idle at? if i let my truck move long enough at idle it will shift into second at around 10mph. this normally happens when i'm moving slow in traffic.

 

Im gonna have to find out where it idles at from him and get back to you thanks, check this weekend I should have an answer from him by then.

 

Most likely a vacuum leak, and it might be inside the brake booster. Use a 3' piece of garden hose as a stethoscope to listen all around the idling engine for a pronounced hiss. Also check under the dash where the brake pedal pushrod goes thru the firewall.

 

hmm idle air control stuck maby? a vacuum leak is easier to find if you spray something like carb clean around the motor and if it idles up you hit the leak.