Have an 06 with the 4.7 HO truck seems to run fine until I really get into the gas and then it seems to cut out. Runs very smooth at half throttle or less but when you really step on it is when it all goes bad. Gona change plugs but I really dont feel like thats the problem it runs so smooth until you get on it. Wondering if I need to run premium fuel in it? Gona try that on my next fill up. Just cant believe that 87 fuel could cause it to run so poorly at high rpms though. Any ideas would be greatly appreciated.

 

From what I remember, the HO motor does requires premium fuel.

 

100% indeed says right in the Manual, 91 or higher octane

 

and because the PCM is seeing too much knock, its compensating and trying to keep your engine in one piece.

 

I would say, try some 91, or 93 octane, check the plugs.

Biggest issue our truck has is the throttle body sensors. Best bet is to remove the throttle body and clean the snot out of it. Be careful with the sensors they are delicate. Best just to remove them and clean them separate.

Also unhook the battery when you do this, it will help the computer relearn and clear up any codes and parameters.

 

I have to run 91 in my HO other wise it will ping, but thats only b.c of my sct tune. on a stock motor/pcm try cooler plugs. or a 180 tstat.

 

My buddy believes I have a plugged converter? Any chance it would cause it to miss like that only when I'm standing on the throttle?

 

a plugged cat will smell like rotten eggs and choke out at high rpms.

 

My 05 with the HO ran best on 93 octane. It cost about 20 cents more per gallon, but got about 3 more mpg's to compensate for it. I put iridium plugs in mine and that took out all hesitation and lag. Not good to run lower octane in the HO.

 

What you described sound like the stumble I have had since almost new. The dealer can't figure it out. I was told it may be the ERG but that is not the cause. I know the feeling all too well of laying into it and it stumbles at higher RPMs and holds back. Worse once the engine is fully warmed up and even worse on hot days. HO engines seem to have this problem more then the standard 4.7. There is a cam difference and some other engine designs that are different for the HO and something there doesn't work well as a unit. I though about going to a Fastman valve Body and new sensors but I refuse to throw money into this crapbox. Hope you find the culprit because I can't imagine how nice it would be to have the dam thing run smooth and strong sine mine never did.