I have a 5.4l and recently it started making a lot of knocking noise. Sounded like litters or valves. The panel shows no change in oil pressure when the noise occurs. The noise comes and goes. Seems to happen as the engine heats up. Any guess?

 

What oil and filter are you using?
How many miles?
Could be a number of things. Exhaust leak at the manifold, timing chain tensioners, plug about to spit out, misfire etc...

 

Mine had a noise like that, sounded like a combine on cold starts . Turned out to be the cam phasers(timing chain tensioners ).. So bad it just about took out the oil pump from the chain grinding on the housing and block face. I had the whole motor re-built at 105k.

Dealer diagnose it and suggested to drop a create motor in for the tune of 8k.
I found a good reputable guy to re-build the org for 4k and it was the phazers that failed.

 

Maybe check and re torque your spark plugs. I had a sound like yours and i blow a plug in #7 and now that its fixed the sound is gone. I also replace all coils maybe that was my problem with the noise that's something to check. My trucks at 98K

 

2000's don't have cam phasers.