Acceleration issue

[Mattmo99]

Hi everyone I’m new to this site so hopefully you guys can help me out I have a 99 explorer 4.0 sohc runs and drives fine until 3000rpm under hard or light acceleration soon as it reaches 3000rpm it bucks while still holding its load so basically it’s almost as if it’s bouncing off a rev limiter while driving, lots of new parts in it timing was just done and double checked by a ford tech, have a new fuel pump new fuel filter new plugs that are motor craft new wires and new coil, coil is not a motor craft so maybe that could be it? Otherwise also has new DPFE sensor new maf sensor new cam sensor new throttle position sensor can’t be the trans range sensor due to I’ve tried starting it in drove and in reverse and no luck and reverse lights come on when in proper gear, pulled off upstream O2 sensors to check for clogged cats and even did a backpressure text on it and passed that with not even a psi of restriction this thing is driving me nuts just want to drive the thing already also has new upstream O2s as well and new intake gaskets fuel trims are fine isles great no check engine Light shifts fine just soon as I come up on 3000rpm I get nothing any input would be appreciated thanks!

 

[1998Exp]

Hi everyone I’m new to this site so hopefully you guys can help me out I have a 99 explorer 4.0 sohc runs and drives fine until 3000rpm under hard or light acceleration soon as it reaches 3000rpm it bucks while still holding its load so basically it’s almost as if it’s bouncing off a rev limiter while driving, lots of new parts in it timing was just done and double checked by a ford tech, have a new fuel pump new fuel filter new plugs that are motor craft new wires and new coil, coil is not a motor craft so maybe that could be it? Otherwise also has new DPFE sensor new maf sensor new cam sensor new throttle position sensor can’t be the trans range sensor due to I’ve tried starting it in drove and in reverse and no luck and reverse lights come on when in proper gear, pulled off upstream O2 sensors to check for clogged cats and even did a backpressure text on it and passed that with not even a psi of restriction this thing is driving me nuts just want to drive the thing already also has new upstream O2s as well and new intake gaskets fuel trims are fine isles great no check engine Light shifts fine just soon as I come up on 3000rpm I get nothing any input would be appreciated thanks!

You already threw every possible part at it. How about taking a ride with a good scanner, and actually recording what's happening when it gets close to 3000 RPM?

 

[Mattmo99]

You already threw every possible part at it. How about taking a ride with a good scanner, and actually recording what's happening when it gets close to 3000 RPM?

I have a snap-on ethos pro I’ve been using and I’m limited to my data stream but from what I can see everything I checking out good took it to ford and they can’t even figure it out and I’m not gonna keep paying ford to just check something

 

[donalds]

Bad capacitor in the computer worth a look

 

[Mattmo99]

And how would I go about checking that?

 

[donalds]

Remove the computer and look inside

 

[1998Exp]

Remove the computer and look inside

Highly unlikely to tell you anything about a bad capacitor, unless it's charred from an internal explosion. Some electrolytics do that, but most just dry up and severely degrade without any physical signs. However, it's not a bad idea to look: you may see obvious discoloration on the printed circuit board, a cracked resistor, a broken copper trace, something desoldered, or even bubbling on an overheated integrated circuit. Barring all that, and assuming that it passes the self-test (it would set the CEL if it didn't), the only practical way to tell for sure may be to substitute a known good one. I believe that remans are available; or you can get one cheaper from a JY; just make sure the model year, engine, etc. match. Unfortunately, a 1999 has PATS, so it would have to be programmed to your keys before it can start the engine.

 

[donalds]

Highly unlikely to tell you anything about a bad capacitor, unless it's charred from an internal explosion. Some electrolytics do that, but most just dry up and severely degrade without any physical signs. However, it's not a bad idea to look:

Therese computers are known to fail due to a bad cap usually they leak a refurbished computer will just have new caps and a self test
Thanks for the long version of my answer