Good morning fellow F150'ers,

I'm going to try and efficiently explain my situation.

Truck Specs:

- 222,000 miles
- 5.4 v8
- 4x4
- SuperCrew

Repairs within last 12 months:

- replaced intake manifold
- replaced all spark plugs and coils (all Motorcraft)
- replaced AC compressor
- replaced two fuel injectors
- replaced fuel filter
- replaced front brake pads and rotors

Issues:

- intermittent shutter when in overdrive. After the truck / transmission is warmed up, issue goes away. This tends to occur 40mph+ and rpm range of 1,500 - 1,700 RPM's

- downshifting at highway speeds to pass other traffic doesn't accelerate the truck. The truck acts like it would if the fuel filter was clogged... it barely wants to maintain speed (especially if trying to accelerate during an incline)

- delay in shifting from park to drive (especially after the truck has sat overnight).

I took it to a transmission shop yesterday afternoon and had them look things over and test drive the truck. They said they weren't confident it was a transmission issue and thought either something with the engine or possibly signs of cloggs cats.

I'm at a loss as to what to check next. I'm willing to replace the transmission if that's what this calls for as a resolution ... same goes for replacing the cats... i just can't afford to be wrong and have to do both if that makes sense. I will admit right now that I have not dropped the trans pan and replaced trans filter / fluid. Any advice would definitely be appreciated. Thank you in advance for the

 

I'd start with a fluid and filter change on the transmission 4.8 quarts mercon V

 

Look at your EGR Valve. If it is dirty and not working properly it can cause the problems as you describe. You can clean the valve rather than replace and check the line from your manifold to the EGR. If you hold your hand next to the EGR (dont burn you hand ) you can often feel it open and close when you give it gas. This can telll you if it is working.

Also, the trans service as recommended above is a good idea.

 

thanks for the feedback thus far guys... I'll definitely do both.

Any thoughts on catalytic converters being part of the issue? I'm honestly not sure how to diagnose a bad cat.

 

I'd check your fuel pressure first. Make sure it is proper pressure and volume. At least 30psi under load. Second would be to test the cats. Either have to drop exhaust down a bit and drive. Loosen the 4 manifold stud nuts (depending on rust). Pull both upstream O2 sensors and check pressure with a gauge. It sounds like you are on the right track. Can't believe the transmission shop didn't check those couple things in their diagnosis.

 

Yes. I recently diagnosed this for a friend. He had the same symptoms you have, except for the delay...it might not be related. We replaced a bunch of engine components that were due anyway.

One cat was the culprit. If you have an infrared thermometer, you can use it to diagnose the cats, the meter I bought cost $11.99. Google a "how to". You'll need a pen and paper when getting temps to write them down. Before and after the cats.

Otherwise in the dark, cruise the highway a bit and then park. See if any cats are glowing red.