2010 5.4L 3V Rough Idle - Help
 

Hi Folks,

Read a number of helpful threads related to my issue, still no luck. Any help would be greatly appreciated.

Back in may, my 2010 F150 5.4L 3valve through a P0345 bank 2(drivers side) with a P0349 pending. I added oil (was at half mark on dipstick), and cleared codes. They never came back, BUT:

• Over the last 4 months, have developed constant rough idle when hot outside and when oil was fully heated up. Shakes the whole truck! Would always clear up once driving (increasing RPMs).
• Recently put on new motorcraft plugs (originals had 74K), and the truck idle got a little worse now. Missing at idle and when accelerating.
• Replaced Driver side VCT solenoid. No change to rough idle. Old solenoid had no damage, no dirt/sludge in oil passageway.
• Never missed an oil change, always used synthetic, always used motorcraft oil filters. Currently at 75,000 miles.
• Cleaned throttle body and maf.

Should I bother replacing the passenger side VCT? Should I replace all the COPs? Any ideas? Some threads mention:

- Alternator diode issues could cause this.
- Bad alternator ground issue.
- Bad cam position sensor.
- Bad cam phaser?
- Bad alternator ground

Thanks for your time and help.

Rather than continue to throw parts at it, sounds as if it needs to be diagnosed by a technician.

As per Google search ...

Battery checks out good.


Visual inspection of the wires and connections to cam position sensor and alternator look good.


I haven't had the best luck getting the truck fixed at the dealership in the past. But may have to give it another try. Alarmingly, after the plug change the truck is now running rough at speed and idle (before it was only at idle). Was thinking COPs, but don't want to keep pumping money into it.


I will report back on what is found.

Does it make a knocking noise at idle as well? Sounds an awful lot like camshaft phasers heading/headed south.

how in the heck does a faulty starter motor have anything to do with his symptoms?


You aren't throwing any codes? even if the light on the dash isn't on, hook it up to a scanner (free at auto parts store) and see if anyting is in there. Could also be MAF issues. Pull it and see if it is clean and/or clean it with MAF cleaner.

Ask the interweb. As noted ... The "possible causes" are verbatim as per the "Google search".

As per the related ...Reference: -REFERENCE-
.

Yep, cleaned out the maf, it looked great, but cleaned it again anyhow.


Yes, making a knocking noise at idle as well...can feel the vibrations through the valve cover, but I have heard worse coming out of these 5.4's...

Interestingly some folks have indicated in the past, mostly mustang forums, that alternator diode issues caused some electrical voltage issues that caused rough idle etc. I had the alternator tested by a mechanic, said it was ok, but I was tempted to go ahead and through a used one ($60) on it to test this theory. Just as long as its not a low oil pressure issue.

I have heard varying degrees of knocking from these things from bad phasers. I have done timing sets and phasers on probably well over 100 of these by now. Some are worse than others.
Sounds like this is your issue. Do yourself a favor and if you do phasers do the whole timing set (chains, tensioners, guides) while you are in there. I have had MANY with cracked or completely broken guides, blown out tensioner gaskets, etc.

Before replacing the timing set check the hot oil pressure. If it is not 30psi at idle consider installing the Livernois cam phaser lock-outs while you are in there.