Vehicle: 2003 Ford Expedition XLT Triton V8 5.4, approx 145,000 miles

I have owned this vehicle for about 6 months and started to have some issues where it seems the vehicle loses power at random, or will simply run kind of rough. So far I have installed new spark plugs, coils, new PCV valve, removed and cleaned the idle air control valve with carb cleaner, cleaned the throttle body, checked for vacuum leaks (haven't found any, not ruling this out yet though), cleaned the MAF sensor.

Doing all of the above has definitely made the truck run a little bit smoother, but I am still having issues. There are a few things I noticed, the issues only seem to surface after the engine is nice and warm, during the warm up period it runs like brand new.

There are three different things that take place:

1. Sometimes when accelerating, not accelerating enough to make the transmission downshift you will feel the engine lightly shuttering, as if it is having a hard time getting power. This also tends to take place when climbing a hill.

2. You will be driving, everything will be ok, then all of a sudden it will lose power for maybe a little less than half a second, I've actually watched the RPMs drop almost to zero while this happens. Sometimes this is accompanied with a backfire under the hood.

3. When idling in gear, the truck shakes ever so slightly. Nobody notices this but me, but I can feel it.

I am not a mechanic myself but am pretty good with this sort of stuff, I also have 2 different friends who are mechanics and they are stumped. I'm hoping that someone else has experienced this issue and might have an idea of where to look.

 

I have an 07 5.4 thats doing the same thing. I know this post is old but, dis you figure it out.

 

First thing to check is the fuel pressure.

 

Ill try to do that today on mine. Thanks a lot!