I have 07 sscrew with 5.4. 93,000 miles. At start up truck runs perfect. After 20-30 minutes of running motor will start to start running rough at low rpm. Diesel sound. I can rev up and motor clears up and idles fine. Should I replace VCT solenoids? Or phasers? Or both at one time?? Help its driving me nuts!!

 

If you're thinking that's what it is...which is likely, then I'd start with the least expensive part first. VCT solenoids.

 

I think the same way. However, to replace VCT solenoids on an 07 you have to remove valve covers anyway. So I figured do both. I just drove it on a short errand and it sounds like a new truck. Runs perfect. Only after heating up is when it will idle bad like a diesel. Rev it up and it goes away. All good maintenance.

 

Very frustrating.

 

Thinking on this more, I'm curious if a vacuum leak could attribute to this. Leaking might not form until the hose warms up and expands slightly.
Just an idea...thinking out loud here.

 

I checked all lines I could. I was thinking same thing. From what I've read on other posts it sounds like classic phaser issue, but it doesn't do it until it reaches a certain temp. I pulled oil pan and wasn't all that bad. Had engine flushed out and new oil and filter.. I know solenoids have screens in them where oil passes through. Maybe one has some debri on it. I'm probably gonna replace vct and phasers just to be safe..

 

Oh yea and no codes are showing up...

 

Check the crankshaft endplay. They had problems with the thrust bearings in 2007 wearing out causing the crank to walk and lose oil pressure. Was there any metal in the pan when you had it off? Oil pressure at hot idle should be minimum 25psi.

 

To test for VCT noise:

1. Place the transmission in park or neutral
2. Bring engine oil temperature to 160° F (71° C) or above as indicated by the scan tool "EOT" PID.
3. Allow engine to idle, and determine if noise is noticeable.
4. Set engine speed to over 1200 RPM (if noise is a VCT knock, the noise should disappear).
5. Return engine speed to idle (verify knock returns).

If the noise intensity is more than a lightly audible knock at hot idle under 1200 RPM at engine operating temperature, replace the cam phaser

Hope that helps you figure it out

 

Usually, the diesel noise happens for the first 2-3 seconds after start-up, then goes away. As the phasers get worse, it does as you described. Eventually, it causes the timing chains to beat the heck out of the guides, then they fall apart and clog up your oil pick-up tube. And finally, your engine self destructs! This is what happened to my truck - except for the self destruct part. The solenoids never did get replaced and are still fine and it runs good now ($2600 later). It sounds like phasers, both timing chains, gears, tensioners, guides and oil pick-up tube to me. That was my fix and Ford did all the work. Good luck.

 

what was the outcome,solinoid or phasers?

 

You do not have to remove the valve covers to replace VCT Solenoids on any 5.4L 3V! If it runs fine at start up then warms up then it could be a lot of stuff, but I am leaning towards vct solenoid. Unplug and see if it runs better!

 

i have the same problem. i changed solenoids, phasers. and timing chain tensioners. 600-1000 rpm hear a tick noise then let off runs rough. give a little gas and clears up...totally confused. i unplug solenoid it runs fine

 

is unpluging the vct solenoids an accurate test? or does it only work for a specific problem with the solenoid

 

i think it's an oil leakage problem in the right cyl head. i removed both valve covers and checked for oil flow to both front cam caps. i have good flow and pressure through caps to phasers. i do notice rt cam caps bleeds more than left cam cap. not sure it's a cylinder head issue or a cam issue. by disconnecting the solenoid it keeps the oil constant to cam shaft. when solenoid is energized it changes the flow to advance or retard timing. so by disconnecting just one solenoid in goes in open loop. the truck runs fine and has power. just causes the check engine light to come on and vct won't adjust timing to control egr function. so until i have a some idea how to fix i'll just run it this way until it blows up.