Hello all.
2000 5.4L. My truck hesitates pretty bad when it is warm or if the A/C is on. But it is only AFTER it gets to running temperature. By hesitates, I mean I can shift out of first at 2,000 RPM and it will fall to 15-1600 in second. But then if I hammer down as far as I can without it dropping back into first it will only climb to about 1700-1800. Even going around 25 MPH! If it isn't up to running temperature yet, it would be around 21-2200 while hammered down in 2nd. I've changed the plugs, fuel filter, cleaned the MAF, Gott's Modded it. Could my O2 sensors be going bad and as the exhaust gas is heating up just starting to crap out more??

This issue is driving me INSANE! I hate running A/C for this very reason. OH - I should mention as well that the throttle response suffers as well. You have to pretty much floor it to get it to downshift. Please help!!!

 

catalytic converters?

 

I had high flows put on July of 08. But it did blow a head gasket during October of 08 too.

 

O2 sensors rarely cause drivability issues.

More probable is a restriction in airflow (either intake or exhaust), un-commanded EGR flow, vacuum leak, low fuel pressure, etc.

Do you have a CEL?

 

I do not.

 

when is the last time you changed the plugs, what were they gapped to and what brand of plugs and cops are you running?

 

Motorcraft plugs. Changed em 8,000 miles ago. Have never changed the COPs though. I had one crap out on my then so I replaced just it. Never 7 i guess (3rd back on the driver side.) Is it possible the COPs arent firing as hot and its taking a toll, or do they either fire hot or not at all?

 

try swapping another COP with the faulty one and see what happens

 

I already have. I have 7 stock ones in and 1 aftermarket.

 

then swap an injector

 

Does your CEL work during prove-out?