'05 SuperCab F-150 XLT (4.6L, E4OD), 66k miles

Sometimes when at a stop sign I feel the truck shake to a certain degree. The tach doesn't appear to flutter any - I couldn't really say that I feel it in the engine (though I don't really know). All of this is with my foot on the brake with the truck at a complete stop. The truck runs/ride smooth going down the road.

I've been hearing that the quality of gasoline in my area (or maybe everywhere) - northeast Texas - is not so good, so I'm not sure if I should just write it off to that or explore other options.

Other possible symptoms/info: A few tanks of gas back I noticed my mileage and engine power were both going way downhill. I went from 16-18 mpg average down to 13mpg. I ran a couple of more tanks through it and the last tank I ran almost completely empty (hoping to suck any bad stuff out through the filter). I filled up, changed the fuel filter, and put a bottle of 91% alcohol in the tank.

The air filter looks good, and I've not seen a service engine light or any other signs of trouble. The truck has been serviced very regularly. I remember on my old truck a stuck EGR would cause the engine to flutter but I don't have any experience with this newer one.

The shaking doesn't occur everytime I'm at a stop, but I seem to notice it here more lately.

Thanks in advance for your help!

 

My '01-4.6L, '04-5.4L, and '07-5.4L do and have done it. At a traffic light or sign, it's almost like it skips a beat now and then. Not every stop, but it will occasionally. Similar to, or maybe is, a misfire.

I should say that it is not a constant shake...but instead feels as if one cylinder misfires one time...kind of a 'wobble' then smooth. Then it may not do it again for a week. My '01 was the worst...punch it through a block, come to the stop sign and it was like it was skipping for about five seconds, then would smooth out. The '04 and '07 only do the "one miss" type shake.

 

it's the motor, not bad gas. My Mustang with the 4.6 does the same thing...especially when not in gear.

alot of the 4.6 guys here have said theirs idles kinda rough. if your still under warranty, take it to the dealer and tell them it's a "Driveability" thing. they'll check to see if you have the latest ECM flash, and probably tell you there is nothing wrong.

you could also need a tune-up. Ford says the plugs are good to 100K, but that is BS. I've seen plugs go that long before, but the motor ran like crap. Once the plugs/wires were changed, it ran like a champ and purred. (4.9 with 127k on original plugs)

oh, just saw you have 66k

 

I'm going to pull a few spark plugs and have a look. What is the proper gap on these?

 

take it to the dealer there is a tsb about replacing the plugs. also the plugs do not have a gap the electrode goes from one side to the other. they cost about 15 bucks a peice. and you need a 9/16 plug wrench and the motor needs to be warm when you try to remove them. if you break the plug it takes some speicial tools to get them out. and they are known to break off.

 

he has the 4.6L engine. the problem you speak of happens with 5.4L engines.