ticking/knocking noise under heavy acceleration

[extrabitching]

Hi, I have recently developed a new engine noise on my 2000 5.4l, 200,000 miles and running strong. I only started noticing it recently after doing quite a bit of towing of a heavy trailer. When accelerating I would get a knocking or loud ticking, almost like a vibration noise but nothing is loose or vibrating. I never noticed it before doing the towing. Now without the trailer I have the noise but only when really getting on it, or when it down shifts like if passing, or when I am getting on the freeway. It is not there at idle or anything like the common ticking complaint, doesnt happen if revved in park, only under heavy load like towing or hard acceleration. My first guess would be a worn timing chain or guides or tensioners and wonder if anyone has experienced this noise and fixed it. Would it be possible to have caused this by towing a really, really heavy trailer. Definitley an engine noise, not exhaust or loose plug or anything.
Any advice is greatly appreciated.
Mark

 

[FordandPolaris]

Did you look to see if one of the studs broke that hold the manifold to the block? I know you said it wasn't an exhaust leak, but that can cause what sounds like a vibration and is easy to overlook.

 

[harley91]

Could be spark knock. Hard to tell without hearing it though

 

[alaskanexpy]

sounds to me like your about to blow a spark plug. i've blown one and almost blew the second caught that one in time! check all your plugs right away.