Mine is a year old with 10k miles and it hasn't changed one bit since the day I drove it home. It is related to the low idle speed. Slowly press the gas pedal and raise the engine speed 50-100 rpm and it smooths right out. Mine smooths out when the AC is on, probably due to the slightly higher idle speed and the extra rotating mass. Had one reflash for the concern back in December without any change at all. Maybe one of the new flashes will help. Sometimes when I'm sitting at a light with some friends in the truck and the AC off, I'll ease down on the gas pedal just a little to smooth it out because it's kind of embarrasing in such a nice truck...

 

Think it may have to do with the odd number of valves per cylinder? 3V, although allowing relatively miserly (ford's actual word in one of their advertisements) fuel economy for an engine of this power and displacement may contribute to an odd spark plug firing or combustion chamber activity. I'm curious if the 4.6L does this at all.

 

Oddly, the 4.6 idles smooth as glass. Our '02 (2-valve) Expy with a 5.4 had a little vibration at idle. Whoever mentioned the low idle speed has it nailed, i think.

 

Yeah, but the question is why not when. These things idle at 700 RPM, it's not low when compared to most other cars out there. Why does this idle speed cause vibration? the great mystery of life continues...

 

I have the 4.6 and it was as smooth as glass, until it was reflashed. Just wondering if I need to disconnect the battery and let it start over on the learning curve.

 

That might help- it needs to "relearn" it's optimum idle.

 

Thinking about this whole thing yesterday when I remembered that my engine is not exactly stock. I added a helical intake spacer by Airaid shortly after I bought the truck. Maybe that is what has cleaned up my idle.

I still can't quite bring myself to add the Predator tuner, so many of the bothersome elements of these engines could be cleared up with one. Just not that comfortable spending more money on a leased truck.

This will be my last post as a resident of Saskatchewan. Moving back to my home province of Alberta next week. If I'm going to take the plunge I'll have new tires and a tuner by this time next week as I'm actually temporarily moving to a city, Red Deer, with a Cooper Dealer and a Diablosport dealer.

 

I had the rough idle with hesation when mashing throttle and what i felt was poor mileage my dealer reflashed with no hassles and made a big diff. I have gotten this big beast up to almost 21 mpg on the highway at 70 mph and cruise set 20.9 to be exact

 

I have an '04 F-150 XL 4.6L that has a vibration every 3 to 5 seconds. If I am at park and idle, sitting in the driver's seat, I can feel it... it is there clear as day. I have 21K on the engine so I doubt it is a 'break in' issue. I had the mechanic at my company sit in the truck and without hesitation he said it was a slight misfire in the engine. I had the computer flashed in the spring for the lack of acceleration, didn't seem to help much, but then again I never could find the sticker that they are supposed to put in the engine compartment when a flash is made. It is interesting to me that some people say that 4.6's run smooth as glass because mine definately does not. I'll post an update when I get the truck back. Has anyone else taken a 4.6 in for idle?

 

My 5.4 still has a slight vib when stopped at a light. I brought my truck in to have an alignment done after I installed the autospring leveling kit. I mentioned that I was feeling a rough idle and they reflashed the PCM. That was 3 months / 5000 miles ago and the rough idle is still there. I feel that if the rpm's were bumped up by 200 then the rough idle will disappear and it might help with the hesitation of the line.

ox

 

I purchased the Predator tuner on Wednesday and put on Cooper Dicoverer ST's in 235/80R17 on Thursday. Just trying to run the tank out of gas so that I can put in 91 octane and switch to that tune.

For those of you who might be looking for a narrower faced tire the Coopers have about an inch and a half narrower tread face than my old BFG AT's. For the nature of the tread the Coopers are amazingly quiet. Got to love the sound deadening qualities of these new Fords.

The Predator dealer I bought it from says that he has already received assurances that the current units will work with the 2006 trucks.

Red Deer is a boom city with lots of disposable income right now. There are already quite a few 2006 Super Duties on the road. Drove by one of the GM dealers the other day and they had four Hummers sitting there ready to go. Young guys in their early 20's are working on the oil rigs and making $250,000 a year.

 

My 05 Supercrew with the 5.4 also is a bit rough at the first start up. At 3600 miles a fuel injector had to be replaced. Currently it has over 10k after a six state road trip with no problems. Once it warms up it smoothes out. My previous truck was sold with 170k on the 4.6 and it was a smooth idler to the end of my ownership. My little brother owns it now and he loves it.