Help! I have a 97 Ford f250 5.4 L. It runs fine until the outside temp gets above 90 degrees or so, then it won't accelerate and starts smelling like unburned fuel. I had a bad O2S B2 S2, but replaced it. The live data on the scan tool shows the OL fault when it starts acting up. I don't understand why it seems to run fine in cooler weather, but leaves me stranded when it's hot outside. Tried loosening the gas cap to see if pressure in the tank might be the cause, but no

 

Look at the sensors that have direct influence on fueling.
The IAT, the coolant sensor, the mass air, for readings out of spec.
There is a TSB on the IAT causing loss of power when temps get high in the engine bay.
Look at the fuel regulator vacuum hose for signs of fuel in the hose indicating the regulator diaphram is leaking.
Check fuel pressure for being to high.
Good luck.

 

Thanks!!! I actually took it to a shop this morning because I was tired of beating my head against the wall (figuratively). He said the barometric pressure was reading wrong and the truck was running lean for a higher elevation. When it is hot outside, the air is even thinner. After he finished with it, we took it on a long drive and it ran good. The outside temp was about 95 degrees, and usually it would start dying within 15 miles. He charged me 30 bucks!!!! Not bad at all! Going to drive the hell out of it tomorrow, and make sure all is well before I take the rent car back (My daughter doesn't want me to, because it's a '13 Ford Explorer Limited, and she thinks my truck is old and ugly) If it still gives me problems, I will look into your recommendations. Thanks again