I have a 2000 F150 with that has a few problems but this the latest. When I am in idle I can get the engine to rev when I push the gas pedal. But when I put it into drive the truck (especially when first starting up) will not rev up during acceleration no matter how far down I push the pedal. It will then all of a sudden rev the engine but still will not accelerate until the transmission shifts, I will get to full speed. But as I modulate the speed the truck might or might not respond to the pedal again. After I have driven it for about 30 minutes the problem is not as bad. Pulling codes tomorrow but was hoping some one might have some ideas in the mean time.

 

Add more detail. Miles, engine, history of vehicle, recent maintenance. Not much to work on.

 

It's possibly something with the fuel system, but not revving when put into drive makes me think it may be something with the timing chain. Perhaps the timing chain skipped a few teeth.

Another culprit could be with a clogged catalytic converter, but I would think you would have the same problem revving when out of gear.

 

Its got 145,000 miles on the engine. I replaced the fuel pump in 2018, changed fuel filter in 2018 and 2019, replaced IAC because of idle issues. I have a bad O2 sensor I cannot get to so it runs rough to start with. Codes pulled only show the O2 sensor as a problem.

 

A 2000 should have a plain old cable opening a throttle blade. A direct mechanical connection from the pedal to the throttle blade. Have you looked closely at the throttle body and the air inlet? I saw a video where a guy found a piece of foam from inside the fender blocking the inlet to his air filter. It broke loose and wiggled to a spot that cut off air flow.

The only thing keeping an engine from revving itself to death is controlling air flow via the throttle body and blade.

 

I actually pulled all that off and made sure there was nothing in there and that the TB was not dirty. I did not see anything.

 

I reread your post and see that it's only in gear that you have the problem.

What happens if you put it in Low then shift up manually?

 

Yes, how many miles and how long since transmission service.

 

I tried that today and it worked better the first time I tried it, but not the second time.

 

So, what happens?