What makes a 1990 F-150 302 lope when it is at idle?

Answer 1

fuel pump

Not fuel pump. Idle air control motor. Replace or remove and clean. Simple and quick job.

Its normal for this particular motor to lope at idle because Ford used a high rise exhaust

valve which in return required the cam lobes to extend creating a longer revolution than the intake valve. Thus, the "lope" you hear or feel is basically power. FORD POWER!!!!!!!!!!!!!

answer

On fuel injection systems, the usual cause for the idle to hunt, ( idle speed raising and dropping by up to 400 rpm's) is the throttle position sensor. The Idle Air Control sticking would cause the engine to stall and a fuel pump would have a good idle, but no top end speed. Take the tps off the throttle body and using an analog ohmmeter, touch the center pin with one on each side of it. In the closed position, one end pin should be high resistance and the other low. Slowly turn the center knob and watch for a smooth increase or decrease in resistance. If it jumps around, or suddenly reads infinity, replace the tps.