1990 f150 xlt lariat
if I rev the engine or hit the gas while driving then let off the gas pedal, it doesn't gracefully go back to idle. The RPMs will go down gracefully for a moment, then it will sputter and jump back down to 1,000 RPM and return to a smooth idle. To be honest, I don't even know where to start looking. Other than that it runs fine. It just doesn't sound good and I want to fix whatever the problem could be. Where should I start?

 

This forum is for '87-96 trucks. You should post in the correct forum.

 

I I meant to type 1990. I will edit it

 

throttle position sensor and idle air controller (TPS and IAC) are the devices that handle this and one or the other or both may be contributing to your problem. I would start there and work through the tests the manual prescribes. Resistance of the device can be measured as well as the voltage.

let us know what the diagnostics turn up.

Don't be in a hurry to swap parts unless you know the problem is local to that part. Stay with Ford part on the TPS as some of the others are pretty much junk.

 

I appreciate it. I will test both of them. do you think either of them would have anything to do with the fact that after I change gears (I have a five-speed manual) the engine continues to rev at the higher RPM for a couple seconds before it lowers the RPM back down to the new gear ? It doesn't shift hard, it goes smoothly into gear, but the RPMs stay high right after I shift. I'm just wondering if you think either of those things you mentioned would also cause this other issue

 

Anything is possible on an antique vehicle. Read these pages & follow the links in them:

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Put ALL your truck's details into your signature so you don't make that mistake again.