I had a 2004 f150 fx4 it was knocking (which I assume was the cam phasers, as it seems common). It got to where as I slowed down it started it get a rough idle with very loud knocking. It got to the point that the engine ended up dying almost every time I stopped. I ended up trading it off for a 2009 f150 lariat. I've had it for over a year and the knocking in it has gotten louder over time. It's going down the same path my 04 did. I love these trucks, I love everything about them except these engine problems. Has anyone had this same problem? or any advice is welcome.

 

It can be a number of things. Need to have it diagnosed. My 2004 started a "tapping" but got it into the shop before it very bad. Needed new rollers and a cam. Caught it before any valve damage.

 

My truck is doing the same thing to the point where if the RPMs get to around 500 the engine dies out. I took it to the dealership and they wanted 550 just to diagnose the problem by taking off the valve covers. They said it dies at idle because the timing system has failed (broken tensioners, loose/sloppy timing chain). I have also found shimery oil whenever I do an oil change indicating that something is rubbing and shaving off metal. I'd take your truck into the shop before it gets this bad. I was always told the tick was just cosmetic but now im trying to decide whether I should replace parts or just get a new engine.

 

Not sure if this helps but the 4.6 3V in my Mountaineer also had a tapping sound. thought it was a Cam Phaser issue. Turned out is was a stuck lifter that started grinding on the cam. The cam and lifter was replaced and the engine is much quieter.