1997 f-150 140.000 miles knocking under load. Changed plugs wires etc.
Guess I should say truck has a 2000 4.2 with 18000 miles on it. Just put it in about 7000 miles ago. Last engine filled #1 cylinder with coolant and seized. Hopeing this is something less dramatic. Just changed the oil and didnt see any signs of foriegn substace.

 

A sort of tinkeling or marbles in a can sound.
Could result from an EGR system problem, poor gas octane, carbon buildup in the chambers, use of additives in the gas, sleight lean condition.

 

Thanks bluegrass. Im not much of a shadytree mechanic so what does testing the EGR system involve

 

If there is no code implicating the EGR system then you may do an investigation to see that the EGR is not heat sensitive from age and sticks to the point that is lets a little gas by it upsetting the air/fuel mixture.
The monitoring the computer does is very good but sometimes a condition comes about that isn't detected until it goes outside of specified limits for emmissions but you may see the result ahead of that time.
The EGR has a large metal nut that holds the pipe on.
There are two studs that hold the EGR to the intake.
These could be pretty well frozen and sometimes takes various efforts to get them out without breaking them or rounding the heads off.
I just went thru my system and was lucky to get them out using heat from a torch on the heads to make them grow then cool to help break the bond with the alum, loosenall lubes etc and praying they didn't break on the way out.
After all is out be sure to use anti seize lube on all threads when re assembling so they won't seize fast again.
You may notice that the bolt tip threads stick through the alum casting and become corroded making them hard to back thru the casting when removing them.
Investigating the EGR takes closely checking the pintal operation for sticking, being free of carbon and that is fully seats when not under vaccum conditions.
I done my system looking for a possible different kind of problem I have but found none. No codes on my problem. It's intermittant in nature.
Good luck.