I hope its simple, but with my luck, I'll need a new engine!

 

me and my friend both have 06 xlt's and have had a simmilar problem except it was the #6 cylinder misfire under load and both times it ended up being the catalytic converters. since then my other side has went bad also, his is still fine. we both bought these truck from the same dealer and they came off the same truck when new. maybe ford had some faulty cats in early 06

 

Well something has to make the cat get clogged, like a faulty injector.

 

My truck only does it after its warmed up. I THINK I'll find out today. After the injector, I don't know where they'll go.

 

NICE....they still don't know what it is.

 

I have the same problem as you do. When my truck is cold and I go WOT, it runs fine. After it's warmed up and I go WOT, it spits and sputters. I changed my fuel filter and it didn't fix the problem. I was going to go plugs and coils next, but apparently that didn't help you. I'm curious to see what it is. Did your engine throw any codes? Mine still hasn't gave any yet.

 

No codes at all. It just breaks up its the worst when it downshifts like to pass someone. I can hear it through the exhaust....and about 50% of the time you can feel it. I called the dealer and he said the broke another plug???? I wonder if they are changing all of the plugs and coils. I feel that I'm gonna get effed somehow.

 

sounds like plugs to me, but with only 30k on it maybe an injector?

TSB 07-24-8

Some 2007- 2008 Expedition, Navigator, Mark LT, F-150 and F-250 vehicles equipped with a 5.4 3V engines may exhibit engine misfire during cruise, rough run, hesitation, buck jerk, with or without diagnostic trouble codes (DTCs).

ACTION:
Follow the Service Procedure steps to correct the condition.

SERVICE PROCEDURE

Use Motorcraft® Carburetor Tune-Up Cleaner to clean engine combustion system.
Disconnect canister purge line from the intake manifold.
Attach a vacuum line to the purge port.
At hot engine idle, allow the engine to ingest about a 1/2 to 2/3 of a can of Motorcraft® Carburetor Tune-Up Cleaner. Use caution not to ingest too quickly due to potential hydro-lock issues. Read the entire label on the Motorcraft® Carburetor Tune-Up Cleaner. Shake the can well before using and make sure to use at room temperature.
Shut the engine off and allow it to soak for one hour.
Start engine, allow the engine to ingest the remainder of the Motorcraft® Carburetor Tune-Up Cleaner.
Reconnect canister purge vacuum line.
Cycle engine between idle and 2500 RPM for about 5 minutes.
Inspect the spark plugs for abnormal fouling.
Replace fouled spark plugs.
Re-gap the spark plug to .035" (0.9 mm).

 

^^^
Interesting. Maybe thats why they broke another plug?

 

Dude, your issue sounds identical to mine. I've just been waiting around for it to throw a code before I looked into getting it fixed. I very seldom go WOT so it's not really an issue to me right now.

 

They just called...4 spark plugs, one injector, and 2 coils. SUPPOSEDLY...it runs like a new one now. I'll see after work!

 

its a dealer and they broke plugs? do they have a clue?

 

Yes, but when the plug is stuck its stuck and nothing you can do but break it.

 

I have heard with time and patience, they are not challenging at all, very easy to come out

 

I still break them from time to time. The TSB ain't perfect.