I have an 02 explorer with the 4.6 and have searched for hrs on here about a rattle or valvetrain issue. im pretty sure the noise im hearing isnt from pinging. When the truck is in park you can not hear any noise. The moment you are in reverse or forward there is a very slight noise, nothing to worry about. When accelerating you start to hear a rattle. The more you accelerate the louder it becomes. Alot of people have this issue but i havent seem to find what the cause of this is.

 

is it a ticking noise?? if so could be exhaust stud busted. not sure if explorer had that problem.

 

Are you sure it isn't pinging? Sounds like ping or an exhaust leak like keith97xlt said. You wouldn't hear either sound unless you have a load on the engine...Can you describe the sound any better? The best description of ping is a sound like marbles in a can.

 

actually it sounds like a tin can. the moment you put it in gear and not move you can hear it slightly and then the more you accelerate the louder it gets. whats weird is that if you goto WOT, its like the noise isnt there. The more i think about it, it seems the sound started after i had plugs put in it. Not right afterwards but sometime after plugs.

 

sounds like small exhaust leak. you cant hear it at WOT over thr roaring od the engine. just check all your manifold bolts. especially the rear most ones

 

I'll have that checked but sure sounds like a rattling more than an exhaust leak. But sounds are hard to describe.

 

i put a stethoscope on it and seems to me the sound is coming from the block. I guess it could be exhaust stud broke on the manifold. I have narrowed it down, i think to coming from directly on the back side of the motor.

 

its usually the rear most studs that break. pain in the a$$ tp get at.take off your splash shield around the wheel. thats the best way to see all of them.

 

My 99 Xploder (4.0 v6) was rattling under similar circumstances and I found broken welds on a couple of the exhaust system heat shields right behind the engine...