Hello,

I recently bought a 2005 F-150 FX4 5.4L. It has 210,000 miles on it already and I have no idea the service history. It has a knock / tap coming from the engine, based on research thus far I am fairly confident it is either a cam phaser or VCT solenoid. Just yesterday it began running rough at idle while I was sitting in the parking lot. RPM's dropped to about 500. As soon as I give it some gas it smooths back out and runs fine. My list of repairs that I will make as I get the money to do so will be:

- clean the throttle body
- new spark plugs and injectors
- replace VCT solenoids
- replace cam phasers, timing chains, guides, and tensioners

Does anyone have any other suggestions that I should add to my list? Obviously this is already a high mileage motor but I'm hoping to squeeze as much life out of it as I can before replacing the engine altogether. As I do the repairs I will post follow ups in case anyone else is suffering from similar issues.

Thanks!!

 

It sounds like you've done your research and have a plan together. I only have a few things to add, and they're just advice, so take it or leave.
Clean your mass airflow sensor while you're cleaning the throttle body. Make sure you use the proper chemicals for the TB and mass airflow sensor. I would replace the throttle body gasket while you're at it, it's cheap.
Since you don't know the service history, check a plug or two before you replace them all. Just to make sure they aren't new.
Replace the VCT solenoids before doing the timing job. Sometimes that solves issues, without having to replace everything. Plus, if you do end up replacing the timing components, you would need to replace them anyway, so it's not a waste of time and/or money.
Make sure you have the right oil filter. Motorcraft FL820S, or a decent one with a silicone anti-drainback valve. No Fram or other cheap brands.

 

Thanks for the reply! I will definitely keep those things in mind.

Right after my first post my truck actually threw an engine code, P0012 "cam timing over retarded - bank 1" so this confirmed I was on the right track with the VCT solenoids. The truck was now idling so rough it was not driveable so I went to my local dealer and got two new solenoids and swapped them out today.

The truck is driving much better, the check engine light went off, and there are no more pending or stored codes. However it's still idling low, around 600 RPM's, even though it no longer feels rough.

Any one have an idea as to why the RPM's are still low? Could this be a cam phaser issue?

 

These trucks idle low, around 560-570. Mine idles at 570. If you get a tuner, you can bump the idle up. A lot of people say that smooths out their idle. They also idle a little rough. Keep in mind it's a big motor, so your going to feel it. You don't want to waste your time chasing a rough idle that's not really rough.