Have a 2006 F-150 with about 207k miles. When stable cruising at highway speeds (about 2000 rpm) with or without cruise, the engine surges or fluctuates. The rpm move is only about 40 rpm, but feels like you are pumping the gas. This primarily occurs when cruising with light gas pedal pressure or in cruise control. Note that there is sometimes surging on lower speed acceleration. It goes away with significant pedal pressure / acceleration or if pedal pressure is removed. Already changed TSP, no luck with the easy swap.
- Cory

 

Did you clean the throttle body and MAF sensor with changing the TPS?

 

Cleaned throttle body, not MAF. Will try MAF clean. Thanks

 

Go to Autozone or other and get your Diagnostic Trouble Codes read, they do it for free and it generally takes just a few minutes. DTCs can be present without a check engine light.
My guess is that you have a coil-on-plug (COP) or injector issue. DTCs P0301 thru P0308 may be present.
Report back with results of DTC scan

 

It sounds like misfire from the description to me. Sometimes these are bad enough to feel but not bad enough to set a check engine code. The usual remedy is to replace spark plugs and the rubber boots on the if it on coils.

 

Did a bit of maintenance. Still chasing issue.
MAF - Cleaned, no luck.
Fuel Filter - Changed, dirty yes, but no luck.
Spark plugs - Changed, no luck
Fuel pump control module - Changed, no luck.
Did not find any ignitor issues.
Still getting acceleration surges, small but most noticeable at less than 2k RPMs.
VVTs or associated wiring? I checked for any frays or other damage to VVT wires, but nothing apparent. VVTs were replace about a year ago. (Note: Have had VVT type symptoms twice in the last two weeks, a very uncoordinated idle that sounds really bad occurring when slow after highway driving, but you can reset with a bump on the accelerator.)

 

no new boots/springs (and clean coil tabs)?

did you do throttle relearn after All this work ?

 

Boots / springs checked and cleaned. Throttle relearn was done again. Fluctuations in accelerator continue and seem to be noticed in most regimes.
Worst fluctuations noted while towing.

 

Still chasing fluctuation, replaced the coils and the plugs. Engine runs smooth, but still fluctuations while cruising along after warm up. (noting no noticeable fluctuations when engine is cold.) Still no codes.

 

Not to scare you, but thats how it started when my tranny began to slip. Small fluctuations that slowly turned into slippage