When I'm driving normally and the truck downshifts (going up a hill etc). It falls flat on its face then goes on fine: kind of like a poorly tuned carbureted vehicle that hesitates when you open up the secondaries. Any ideas what is causing this? I've tried the throttle response fix and it didn't do anything. Thx

 

When was the last time you changed the spark plugs? How many miles are on it? On a flat surface if you stomp on the gas what happens any hesitation or any sort of delay at all?

 

Don't wanna hi-jack the thread but when accelerating my 08' 5.4L will fall flat on its face for a brief second then pick up and be fine. Seems to only do when its a harder acceleration.

 

Original plugs. It runs like a scalded dog when you hit it. 78k miles. I bought it new and it has done this since about a year after I bought it, say 12-15k miles on it. Programmer didn't help it. No codes & no miss. Just annoys me!

 

Country boy change your plugs I had the same problem. Wasn't bad enough to throw codes but sure fixed it when I changed them.

4Nw
I would search threads on checking your plug wires.,With the amount of problems our trucks have wi

 

With the plugs I'd change them before they get stuck. It could be like my problem not enough misfire to throw a code. What tuner u have?

 

Hypertech.

 

Not sure if you were talking to me or not. But I don't run a tuner at all.

 

sorry about that I forgot to quote. I wasn't talking to you on the tuner. Good luck on your findings. Let me know if it solves anything.

 

It might be a transmission lag, when i put the edge programmer in my 07' that went away. Drove me nuts, i was starting to think my trans was on its way out..all is good now unless i switch it back to stock program and it comes back. It is like it is trying to figure out what gear to be in or lock or unlock the converter