My dad's 1989 F150 started jumping to 2500-3000 rpm's while driving. He is the original owner and has done all the work and maintenance on this truck. The truck has a 302, 5 speed, manual hubs and an XLT. I think he has around 190,000 miles on it.

He and mom don't have a computer, which is why I am asking this question.

He said the rpm's jumped to 3000 and acted like the cruise control was engaged. After turning the engine off and restarting it was ok for a few miles and then went back to doing it again.
Since new this truck has been slow in dropping rpm's when shifting. The dealership told him the tach was off, and did not want hear about the motor sounding like it matches the tach.
.
So far he has:

disconnected the cruise

Checked all the vacuum lines

replaced air by pass valve

He has no way of checking psi or electrical issues (he only has basic volt gauges)

Any thoughts, cures or ideas will be greatly appreciated, other wise mother may get her way (she does not understand about old Fords being family).


Thanks,
Patrick

 

Ford Fuel Injection » Throttle Position Sensor (TPS) Here is a link on how to test the throttle position sensor, yours may be bad.
Also if you click on "self test" from the list on the right of that page you will be able to check for any trouble codes.

 

Just talked to my dad, he replaced the TPS and he said it runs better then new. He is thrilled, mom is not.

THANKS!

Patrick