2000 F150 5.4 4x4 supercab, 4R70W, 3.55, SCMT1715 on 87 program, no DTCs

Just had engine rebuilt around 5K ago because of coolant leaking from intake manifold gasket into cyl 1 and causing a head gasket blowout, oil and coolant mixed, and the engine burned a lot of it since I couldn't get it to the shop for a while.

I just replaced the cats on both side and it definitely helps when the engine is cool and at low RPM.

When the engine is cold, it has plenty of power. After it warms up, it has power right off idle, but as the RPMs go up, you really don't get anything else.

For example, I'm pulling a hill empty at around 40MPH and 2000RPM. I give it more throttle and get no more power until it downshifts. Or on the highway, cruising at 55-65 in OD. I apply throttle up to the point right before downshifting and get very little. It still downshifts all the time on the highway for small inclines.

Here's my theories-

-Driver's side O2 sensor could have all 89K on it and it's Fing up the fuel/air mix. I figured that it would throw a code though. Passinger side is brand new.

-When the engine was rebuilt, they had to mill the heads. Perhaps they had to take so much off that the compression is up to the point where the ECU is retarding the timing back really far. So next fillup, I'll use 93 and see if that helps.

-Put LT265/70R17 BFG ATs on 5K ago. That's the stock size, but the originals were P tires. Perhaps tire weight is Fing me.

-Some other mystery part is screwed. IDK

Let me know what you guys think.

Mike

 

Perhaps the fuel filter is partially clogged?

 

I changed that before I started on the cats. I'm going to check the fuel pressure as well.

Mike