2003 4.0 very sluggish after warm up

[FordFlintrock]

Running rich me thinks not. You would be seeing black/wet spark plugs, glowing cats, exhaust smell, black smoke. Running lean one or more cylinders more likely and would explain the calculated load, such as running on 4 cylinders or just one bank.

 

[FordFlintrock]

it feels like it's trying to pull an elephant up a hill! It has a little power at take off, then 2-3k it falls on it's face,

So, I have been doing a ton of reading and I think I may need to do a fuel pressure test while it's running down the road. Maybe the old pump starts performing bad under load???

Install the pressure tester under hood in a safe place. Take it for a road test and at 2-3k when at its worst turn key off with foot still on accelerator and coast to side of road, read gauge.

 

[2003 Blue Explorer]

So, this morning on my commute, I get the “check fuel cap” light to come on. This has come and gone for years and never really been a problem. But, maybe it’s related?? I have no idea, but maybe someone else does? We replaced the fuel cap years ago when it first started illuminating, but it did not cure it. It’s just been an annoyance really. Never caused a running issue, but thought I would add it to the conversation.

 

[Stynx]

So, this morning on my commute, I get the “check fuel cap” light to come on. This has come and gone for years and never really been a problem. But, maybe it’s related?? I have no idea, but maybe someone else does? We replaced the fuel cap years ago when it first started illuminating, but it did not cure it. It’s just been an annoyance really. Never caused a running issue, but thought I would add it to the conversation.

So did you check it? It might also be some esoteric problem with the evap system that is showing up because hey the car is twenty years old.

In any case it's a clue so start digging!

 

[2003 Blue Explorer]

Well, it never got better, nor did I spend much more time diagnosing it. The torque converter took a dump and it hasn’t moved since. The transmission is in my shop currently being dissected when I have free time. Which ain’t much. It’s been there since Sept 17,2024. Real kick in the head.

 

[2003 Blue Explorer]

Transmission rebuild finally done, and driving well in that regard. But, the power issue has worsened since it was parked for a while. Still thinking injectors since it is sputtering now.