I have a 91 F150 4X4 4spd with a 5.0 that intermitantly surges only when driving not when idling. I tested the TPS and EVP (EGR) and all is good. I pulled out a code 63 and 31 from the ECU. The truck idles rather high. Also, there is no vaccuum coming from the vaccuum line that attaches to the EGR even when idle is increased.
Any help would be appreciated.

Mike <!--IBF.ATTACHMENT_563-->
<!-- THE POST -->

 

61 - ECT sensor is less than the Self-Test minimum of 0.2 volts. Have you changed this sensor?

63 - TPS circuit below minimum 0.6 volts. You say you tested the TPS but how did you test it? Measureing voltage at closed and open positions doesn't tell you what it's doing at part throttle positions, and that's where you are having trouble. It should show a smoothly varying resistance when the throttle is swept through it's range, and even if it does it may bve a good idea to try another throttle body or TPS.

 

I tested the TPS with ignition on and TB closed, then at WOT. Both voltages tested good. I noticed that someone had replaced the TPS recently. Also, not sure why the vaccuum line that is plugged into the EGR is'nt pulling any vaccuum when the engine RPM is increased.

Thank you for your help,
Mike

 

Raising the rpm at idle is not going to create the vacuum it needs like being under load at cruzing speeds. The EGR only works at highway speeds/load.

You will need a vacuum pump to check this at idle.

 

1991 F150. TPS problems. Check engine lite on. Either stalls or have to press gas all the way to idle right. Upon shifting 1 to 2, rpm goes low. Question, I have a new TPS, but seems to be under the air intake on the 1991 F150 5.0 engine. Do I have to take the entire air intake off to replace the TPS ?

 

You'll want to take the TB off not the whole upper intake.