I have a 1998 f150 4.6l that will not idle. It starts and if the gas pedal is pressed the truck will stay running, but when let off the truck stalls out? Thank you for any help.

. Replace the Idle Air Control Valve (IACV), clean the throttle plate, and clean the throttle body. Valvoline makes a specialized spray that's safe to use on Ford's teflon coated throttle bodies. Afterwards, clean the air box and replace the air filter.

. Adjust idle rpm to spec.

. Replace the spark plugs, with the same Motorcraft platinum plugs that came in the truck, if they have not been changed in 50,000 miles.