I had originally piggy-backed off of an older thread with this problem child. Figured I would start my own for this.

I have a 2006 F150 xlt 4x4 ext. cab with 5.4 flex.

Purchased the truck at 90k.

At 92k I had to replace valve lash adjusters on cylinders 3 & 4 and cam phaser on bank 1.

At 114k started to get a rough idle after about 10 miles drive time; along with a very loud knock ( like the worst sounding diesel noise ever!!! ). Pulled codes of random misfire, misfire cyl. 3 & 4, and bank 1 over-retarded. Since I had no idea of past maintenance I decided to change the spark plugs... Well, after 7 broken plugs; I managed to get it done. Everything seemed fine untill I got 20 miles down the highway and it did it again... Pulled the codes and got: misfire cylinders 3 & 4, and bank 2 too lean... I swapped coil packs from cylinders 3 & 4 with cylinders 1 & 2... Same result 20 miles down the road same bad idle / knock same codes... I cleared the codes and planned to swap injectors and didn't get around to it. In fact it didn't act up for another 1000 miles. Then it didn't throw a code. I have actually put another 1500 miles so far and have not had a single code or incident. I have driven on several 100 mile trips with no problems.

At 116k the famous valve tick came back. Oh yeah!

AND JUST THIS MORNING AT 116.5k, I head to work and whenever the engine RPM's get to 2200 rpm's there is a loud sound from the engine. Reminds me of a power steering pump running dry only louder. It stays with engine rpm's until about 3000 rpm's. Had a friend hold the throttle while I searched the engine bay. It sound like it is coming from under bank 1 valve cover. It does it cold and warm. No codes, SES, CEL, or any other warning light lit.

As far as my maintenance; I check fluids, chassis, and change oil / filter consistently on schedule. I use Motorcraft 5w20 syn blend and Motorcraft filters. I tend to stay away from the ethanol blended fuels when I can.

I hate to think that I bought myself a bad egg. I know every manufacturer has certain "known problems" with any vehicle made. I really get un-nerved when someone tells me to trade it off. That just causes the same problem for someone else and makes the manufacturer look even worse. Now, as I can not speak for how the truck was treated for the first 90k; All I can tell you is how I have used it and maintained it and don't think that these should be normal problems to encounter.

Any ideas or suggestions? Need more info just let me know. Thanks

 

Here is a recording of the sound. It only changes with engine RPM's and nothing else.

 

OK, two words - "Tension-er Pulley" mystery solved.

Removed serpentine belt, ran motor just long enough to check, NO NOISE, re-checked all pulleys and bearings... Tension-er pulley did have a slight grind to it when rotating. Replacing it tomorrow.