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Ironmike, Ford Technician
Category: Ford
Satisfied Customers: 3385
Experience:  30 years ASE Master tech L1 . Ford master
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F250 SuperDuty Pickup 4x4: 05' F250 5.4 - runs fine cold but

Customer Question

05' F250 5.4 - runs fine cold but after it heats up it has a rough idle but will clear at 1100 rpms.
New plugs - new cam position sensors - new variable cam timeing solenoid on bank 1 - checked continuity on wiring. shops had it for 2 weeks and cannot determine the problem
Submitted: 2 years ago.
Category: Ford
Customer: replied 2 years ago.
Truck has 92K miles
Customer: replied 2 years ago.
It also has a "spark knock" when you accelerate. The rough idle is pronounced and will result in the truck cutting off but when you start it, it runs fine and transitions back to rough idle.
Customer: replied 2 years ago.
I replaced both cam positions sensors about 2 months ago. The truck has the same symptoms but we have tried two new cam position sensors on bank 1 where the scanner says the problem is.
Expert:  Ironmike replied 2 years ago.
greetings, is the check engine light on? what were or are the trouble codes?
Expert:  Ironmike replied 2 years ago.
the 5.4L 3 valves are known for bunch of oil flow /vvt issues
Expert:  Ironmike replied 2 years ago.
best place to start is make sure valve timing is on
Expert:  Ironmike replied 2 years ago.
very easy when using the dealership scanner or an advanced scanner similar
Expert:  Ironmike replied 2 years ago.
we need to check for misfires, relative compression
Expert:  Ironmike replied 2 years ago.
I have seen bad phasers and or the pin to the cam cause valve timing issues that give symptoms like you have
Expert:  Ironmike replied 2 years ago.
If one bank or cylinder head is off/low it points to a phaser/cam out of time.
Expert:  Ironmike replied 2 years ago.
phasers can be replaced without removing front cover. Just need tool to hold chain tight in guide. let me know if the truck chains make noise cold. tensioners can leak
Expert:  Ironmike replied 2 years ago.
every time I have seen cam codes it was a valve timing issue.
Expert:  Ironmike replied 2 years ago.
I helped fix one like this for another shop. I work on fleet trucks and a tech had one like this giving him a hard time and he and other techs had tried a few parts. I did a relative compression test and found bank one had all cylinders low. The pin for the phaser to the cam bent. The shop replaced the cam and phaser and truck was done.
Expert:  Ironmike replied 2 years ago.
how are you making out. any update from the shop?
Customer: replied 2 years ago.
Pulled the valve cover and found an unusual amount baked on oil in the valve cover. Started it with the valve cover off to see if we were getting adequate oil. There wasn't much so the theory was to flush the engine a couple of times to see if this was contributing to the symptoms. Timing chain on that side was tight and no visible issue with the phaser.
Customer: replied 2 years ago.
I doubt this is the culprit but it needed to be done. I'm gonna get it out of this shop Monday and bring it home and install a full OEM timing kit .
Expert:  Ironmike replied 2 years ago.
the VVT system (variable valve timing) works on oil pressure. I did mention that theses are known for oil flow issues. The VVT solenoid mounts into a housing that can get clogged. I have seen oil flushes fix these issues once or twice. The CAM phasers can fail where you can see it and they can also fail where it is hard to tell. The way they design the oil to flow does not help either. The last place to get oil pressure is the tensioner. just before the chain tensioner the phaser gets oil. If the engine has low oil pressure it affects the VVT system. I have seen bad cam journals cause low pressure to the vvt system.
good to start with a base oil pressure test. should have over 20psi hot.