HELP!!! 2002 XLT 4.6 - Engine knocks & Taps at high RPM'S

[modernsigns]

HELP!!
Im new on here! Love this site, it's got tons of great info & people.

I have a 2002 XLT 4.6L V8 with about 120K miles on it. I love this thing. Owned it since it's had 22K miles. I always change the oil before the 3K miles are even up. I always maintain this thing. "YOU COULD EAT OF THE ENGINE" that's how meticulous I am with my cars. I am a DIY guy. Always fix things when they go bad, brakes, batteries, front suspension is all new, egr, crank sensor, new transmission, etc..long story short - I take care of this thing. I now have an engine tapping sound - which I can not figure out.

PROBLEM: My engine is making a tapping grinding noise. It sounds like my valves or lifters are tapping (sounds like marbles are tumbling around the engine). Crazy thing is that the sound is not coming from either valve cover. The valves sound like they are functioning normally.

This marble noise happens cold, warm or hot. Temp does not make a difference.
When I have the car idle'ing I do not hear any noise coming from the valve covers.

The truck sounds like a diesel truck sometimes. The crazy thing is that this sound comes and goes - at all different times and temperatures! It's crazy.

The timing chain sounds fine also. I do not get any noise from the timing chain (front of engine) so I do not think it's the timing chain or guides.

I noticed that if I put the truck in drive and hold the brake (the noise is slightly noticeable --- and if i apply a "LITTLE" gas while holding the brake pedal in drive the sound gets louder and you could hear the TAPPING - TICKING NOISE much louder.

The noise also appears mainly when I am on the Highway (at higher RPM'S) especially in-between gear shifts (when RPM'S change is when the noise intensifies). If I apply hard gas while the engine is ticking the sound does kinda go away. I do not think it's the tranny. Just has it completely rebuilt about 7 month ago and it has been flawless. This issue is definitely an engine noise.

ANY ADVICE WOULD BE GREATLY APPRECIATED!!!! PLEASE HELP. THANKS!

 

[funnyfarmcrafts]

Is it finding overdrive? Do you loose oil when this happens?

 

[modernsigns]

Thanks for replying. The trucks transmission is working perfectly. It goes throught all gears like a champ. Definitely not the tranny.

The problem is engine related for sure. I have narrowed it down to either a collapsed valve lifter, bad timing chain/guides, or worst case scenario bad rod/bearing or wrist pin.

The tapping/grinding noise is consistent with the engines RPM'S. Thanks again very much for your reply.

Someone please confirm this for me. If it were a bent rod - the noise would always be consistent and present. In my case the tapping/grinding noise comes and goes. I am trying to narrow down the possibilities.

Any help would be greatly appreciated!!!

Thank you