2007 Supercrew 5.4LFF Auto

My engine runs rough at idle, even when warm. Has done it since new. It's a mild shake, more like a tremor. (Think "chilly day kinda shiver".) Otherwise, truck runs like a champ. Easy starts, no hesitation, lotsa power, etc.

When I am driving, and I come to a stop light, the engine idles smooth for a few seconds, then self-adjusts to this rough idle. It's annoying as hell.

Dealer says there's nothing wrong because no codes were thrown.

Is this common? Can it be fixed?

Any help would be appreciated.

 

The 5.4 3V tends to have a bit of a rough, choppy idle. I've been told by higher ups that it's in part due to the operating strategy that has the engine running very, very lean at low speeds.

On older trucks, 2004 or so, there were updated engine mounts to help quell the rough idle somewhat, but the newer trucks already have those mounts.

 

Thanks Q.

Unfortunately, I spend a lot of time driving at slow to moderate speeds, so I guess I experience the chop more often.

I thought running an engine too lean too often can cause damage?

 

It's not engine-damaging-lean, just pretty darn lean. I guess in the name of fuel mileage or something, I dunno.

 

My 07 ran smooth and quiet. An open cup of coffee wouldn't even ripple sittin in the cup holder.

 

My 06 Expedition does this as well. It's annoying but I deal with it.

 

i have a 97 with the 4.2 v6 and it is rough at start, after start, sitting at a light and during take off. But does not do it if I put it into park. Is that what yours is doing? I'm try ing to find out what to do to mine. For a 97 it only has 82,000 miles on it.

 

I don't know much about the V6 (honestly, I don't know much about the 5.4 FFV V8 other than what I have learned on this site) but I imagine they are substantially different in how the engine management is set up.

My engine is rough at start-up, and less rough at idle when warm. Putting it in Park seems to have no effect.

My Owner's Manual advises that in outside temperatures above 80 degrees, the engine will run rough for a while (I think it says 10 to 30 seconds) then it will settle down to a smooth idle. The engine does runs smoother after 30 seconds or so, but never quite gets all the way to silky smooth. Also, the initial roughness takes place whatever the outside temperature.

One thing I have noticed, is that the rough idle problem is slightly less apparent as the fuel tank is emptied (curious - fuel pressure, vacuum?). Although even on a near empty tank, the problem still exists.

The rough idle does not appear to effect performance. This truck picks right up from a light, has plenty of power, shifts beautifully, etc. Other than the idle, this truck is perfect.