My buddy's 99 F150 just started to make a knocking noise at higher RPM's. It has a 5.4 with 180K on it. Problem is while accelerating engine runs and sounds fine till RPM's hit from 3 grand and up. At 3 grand there is a knocking noise equal to the RPM of the motor. I thought maybe it was a rod bearing, but to my understanding, a rod bearing would cause a knock all the time. I was sitting on the fan shrould and revved the engine, and when RPM's were around 3 grand I heard the knock. But it was from the front of the engine, around the timing cover. Can a worn timing chain be the problem, or is it a rod bearing?

 

sounds like rod bearing to me. try disconecting one injector at a time and try to duplicate noise. it should get alot quieter in the cylinder that is affected when injector is unplugged.

 

HI!... I had a rod bearing go in my 5.4. It sounded just like that. Quite at idle and low RPM's. Increase RPM's and the knock would get louder as RPM increased.

 

Thanks guys, you confirmed what I hoped wasn't the problem, haha. Guess I'll tell him to save up, get a motor or rebuild kit and ALOT of beer, and get ready for a long weekend in the garage!!