I have a 96 F-150 5.0 5 spd with 333xxx miles. In idle everything seems to work well enough. The problem occurs when I shift. When I shift, let's say at 2500 rpm, I take my foot off the throttle and press the clutch. At this point the engine does one of three things. Most commonly it maintains its rpms for a good 5 - 10 seconds before slowing and returning to idle as the truck is in motion and sometimes it does not return to idle until the truck comes to a complete stop. The second most common is that when the clutch is pressed it will increase rpm by 300 to 500rpm then after a moment slowly return to idle. The least common is the truck will act almost normal and it does this for a little bit then goes back to maintaining its rpm or revving when the clutch is pressed.
I have also taken my foot off of the accelerator and had the truck maintain its speed for at least a city block before decelerating.
It seems that when the truck is in motion the throttle does not respond correctly or maybe the ecu is malfunctioning. I have cleaned the MAF and the throttle body, tested the TPS for correct voltage and resistance. I cannot figure this one out. Could it be the ECU?

 

Could it be worn throttle body shaft or worn throttle blades in the bore? Sounds like it, but what codes have you checked? With OBDII, it should be showing something amiss.

For the throttle body, remove it, and hold it to a light and see if any daylight is clearly visible where the blades rest in the bores.

 

We have six high probability things (IAC, TPS, MAF, throttle body, vacuum lines, EEC-IV) that could be causing this issue ..........recommend getting codes and re-working potential carbon build up in this 333K truck (congrats by the way --- those 5.0s can get 400-500K easy with proper maintenance)

 

Thanks guys I will check these things out and see what I come up with. I appreciate the help!

 

Hello. I am having these same symptoms on a 95 with the 4.9. Did you find the cause? Thanks.