As stated I have a 2008 F150XLT 5.4 V8. Recently it has started making a knocking noise and very rough idle when warm. It only does it when the truck has been driven slowly or typically when going through a drive through. It sounds like a rod knock but putting it in neutral and reving the engine makes it go away for a while. Any ideas?

 

Test your crankshaft and camshaft position sensors. Also try cleaning the throttle body, it may help your car get more airflow when idling.

When was the last time you had a tuneup?

 

i have that problem and have been told that it was a cam phaser. they told me that it was bound to happen and to just use a high quality oil and keep it changed.

 

Thank you, I have heard that the cam phasers can be a possible cause. I just shook my head like I knew what the hell a cam phaser was. Oh well. Waiting for time to tear into it.

 

good luck man. my engine has only got 7000 miles on it and knocks at idle. makes me wonder why they couldnt just stay with the same desighn as the old 5.4s

good luck man. ive heard it could be pretty expensive. makes me wish that they still used the old 5.4s

 

Substitute 1 qt of oil with 1 bottle of LUCAS OIL ADDITIVE.....works great, BTW, use recommended oil, dont switch to thicker weight like a lot of people on here suggest, that does more damage than good.

 

I'm replace my cam phasers as we speak, little did know it would so expensive $2800 later. Could any of you explain this price cause I find it hard to believe even though it is at the dealer ship Ford. But they are doing the timing chain and the tensioner as well. But to me there really should be very little labor for this cause they are right there and exposed. From what I'm see in pic. HELP please

 

ape: How many miles are on the your 5.4L 3V?

The rough idle could be due to a handful of minor issues.-->{Misfire!}--{Dirty Throttle Body}--{Coil going bad}--{Boots on coils bad}--alot of issues could cause this. Heat effects alot of things if these things are not in good condition. I have read about a PCM reflash that solves some rough idle issues.

Does the rough idle occur with the A/C off? Some times I confuse a rough idle with a vibration-->Sorry!

The knock->Many owners have complained about this. Just don't be brain washed into believing your 3V was designed around 5W-20.

I am still trying to find the cause of our 5.4L 3V-->Having a very slight vibration with the A/C engaged-->while sitting still at a stop light.
With the A/C not engaged the 3V is smooth as can be.

 

If it goes away at increase rpm it is oil pressure at idle. The cam journals wear out due to low oil flow to the rear of cams. Then the oil leaks out the journal and the roller rocker lash adjusters start to rattle. On mine it was the right (passenger) cam first. Then the metal goes to the bottom of the engine and eats up the bearings. Take your oil filter to a reputable mechanic and have it checked for metal. If it has metal in it it means a new engine. In my case the thrust bearing was gone and the crank knocked at idle. The crank goes back and forth, floating because the bearing is gone. Ford will blame you for not using 5w20 oil and refuse to fix it. Welcome to the club of 4.6 and 5.4 ticking engines 2004-2008.