The gas cuts in and out unless I am putting the pedal down. When I'm on the interstate I'll set the cruise to 60 and you'll feel the constant fluctuation. It jerks back and forth enough that it feels like its part of the bad suspension.

Could this be a sign that some COPs are going bad, or are dead? I've had the EX for a few weeks and received a P0720 code that cleared itself. The EX died three times, the code appeared, and it ran fine again until the code disappeared.

Also, when I lay into the gas there is a higher pitched sound. Either exhaust leak or something with the drive shaft. Doesn't seem to be coming from the engine bay.

Start suggesting.

 

I would describe bad COPs and misfires as bucking. Sputtering is how I would describe a manifold leak or other exhaust leak.

Also that high pitch noise when you "get on it" could be just the normal sound. When you get that V10 going over 3K RPM it sounds like a banshee, especially with my exhaust system.

Have a look at this thread... https://www.ford-trucks.com/forums/1...mal-sound.html

 

A manifold leak would contribute to that noise too, right?

 

Have you replaced anything since you got it? I would just go to the dealer and pony up the $$ for good quality ones, also replace the spark plugs with motorcraft. Just because the code cleared itself dosent mean the problem went away. How's the transmission fluid and have you serviced it? It could be torque converter shudder. Also check the fuel pressure.

 

Haven't taken it in yet. Will soon though.

 

Not really, a manifold leak sounds like a sputter, not really a whine. Also my new manifold leak is most noticeable right at 2K rpm. When the engine is really racing 3K-4.5K rpm it is very loud. Louder than the manifold leak. It doesn't roar like a V8 does, the pitch of the V10 noise is much higher.

I could try to record some sounds of my truck with my cell phone and post a video, I'm not sure how well it'll come out though. Maybe I should try it with my computer and a web cam.

 

I'm surprised nobody has looked up that code. It's related to the speed sensor and could very well explain the fluctuation when in cruise mode.
Does it fluctuate when you hold the throttle steady and drive 60 ?

the exact wording is: P0720 = Output Speed Sensor Circuit Malfunction.

 

Check the wiring harness to that sensor.

 

Do a search. That is a known issue on Excursions and SD trucks when in cruise. It was addressed in later years. I cannot recall the specifics, though.

 

There were so many p0720 problem threads without the sensor being the culprit that I didn't put the two problems together. I guess I'll go ahead and try replacing the sensor.

 

I had this issue and am very familiar with these simpthoms. To cut it short i replaced all cops and everything is sweet. But before that I spent a pretty penny troubleshoting. Turns out my manifold had a crack, and was leaking into my 8th cop and I also had bad head seal so oil also leaked into the spark ports thus getting misfires. All is well now but it took me some time. My baby is running so sweet now that I'm amazed everyday. While there I replaced all 8 injectors. The fix was simple with a 4in pivot extension for your wrachet.

 

"Simple" is replacing all your injectors, COPs, valve cover gasket and a repaired/replaced intake manifold??

 

Hey 809taino, what did you do to fix the blue highlight? Just tighten the existing head studs? Because that is EXACTLY what I have going on. 3 plugs had oil on them when I did a plug change.

 

Well, I put all new COPs and spark plugs in today. Only had a 15 minute test drive, but it seemed better already. No sputtering in the low RPM range, and it hasn't died yet.