Rough Idle Code P0016

[cmiller1973]

I have a 2008 Exp XLT with 5.4L with 66,700 miles(yes very low) and we are original owners.
Never had any problems until 9/11/23. Wife went to leave and everything was fine. She stopped at stop sign and the engine had a terrible shake. Take off and it mostly goes away. No CEL right away, but then after 5 mins it came on.

I put my diagnostic reader on it and got code P0016. So many said change the CRK sensor. So I did. Nothing changed.
Took it to mechanic close by so I didn't drive it far. He got the same code and a couple others and also a misfire on #3. Advised to do plugs and COPs(coils). 4 hours later & $1300, same issue. I should have done #3 only, but thought it would be wise to do all. He did more digging and found the #3 still misfiring and is only getting 60lb max on pressure test.

He now seems to think it is a valve issue and wants to do a top end job one both heads. Complete rebuild costing at min $6k. Hard to do that and it may be something else, with the vehicle only being worth $5500. I would rather just fix #3 valves. It doesn't smoke, lose oil or burns oil. So we are ruling out ring issues.

Everything I read for the code says cam timing issues and VCT and/or cam phaser. However if VCT or phaser is bad, wouldn't all cylinders misfire on that bank? Odd it is just #3 right? Low compression is weird also. Everything fails but I can't see timing components going bad at only 67k mileage.

I did find one thing interesting. Cold start, the vibration is there but not bad. As the engine warms and gets to operating temp, vibration seems to get worse. In gear it is horrible and engine seems to want to shut off. Shift to neutral, it is not that bad and RPMs go up a little. It also seems to lighten up as the RPMs get over 1200 and runs fine to me.

No crazy noises coming from the engine at all. No chain noise or extreme tapping in heads.

Is there anything else I should be looking at?

 

[Mailman69]

you're absolutely right on the VCT solenoids. My 2008 did the same thing. Start idling rough then give a little throttle and it clears right up. First I thought it was an oil pressure issue which technically it is. Wasn't getting any noise from the cam phasers so knew it wasn't anything to do with that. The VCT solenoids can get clogged up and varnished up Overtime and not have the proper amount of oil pressure going through them to lock the phasers into 0° timing and that's where you get the rough idle. It's got enough oil pressure coming up it's just not getting the oil pressure through the solenoids out to the cam phasers. New ones from Ford or around $102 and the cam cover gaskets, and get this around $120, but the Left Bank is cheaper than the right Bank. I was like don't y'all sell these as a set? Plus there's a sealant that has to go on the cam phaser end underneath the cover and on top of the timing chain cover and it's $65 for a tube. Well hi temp Permatex has never let me down. But the code you pulled on the vcts is correct and that's the way I would go. Unless you're hearing a ticking noise like a bad lifter in an internal camshaft motor, you don't need a full long time and job. This is my third 5.4 and my second three valve. So I got a little experience with them. Hope this helps you out.

 

[peterwells]

So no answers but am having the same issues, when cold engine is fine, as it warms up the idle gets rough, absolutely fine when driving. Idle when warm gets worse as engine is loaded, i.e. AC on, always smooth when out of gear. I would say it is better for a period after a long run, e.g. if I've been on the freeway for more than a few miles it'll be fine at the next few lights. I never feel the engine is going to die and there are no codes.

All I've done to date is ran some injector cleaner through it, it may have made it slightly better, changed the fuel filter (it was old - no change) and replaced some coil and injector connectors that were missing the tabs (no change)

There are multiple threads with the same issue, not many solutions.

if I get off my rear and do some more investigation I'll update.

Peter