engine knock at idle 88 XJ

[Ecomike]

Additives won't help, it's probably piston slap. Many 4.0's have it and it doesn't seem to be a lethal problem for that engine. Keep the oil changed and be gentle while cold.

I disagree on the "additives won't help". Depends on what is causing the noise. With straight motor oil in cold weather mine sounds like a hard starting diesel about to throw a rod. With a 1/2 a quart each of marvel mystery oil and lucas oil additive it sounds like a well oil sewing machine at idle, and totally normal at anything over 1000 rpm.

I have used oil additives since 1973. Only lost one engine in 34 years and that was a dodge 360 V-8 with over 400,000 miles on it before it got rebuilt. Went through a timing chain and oil pump half way through (about 225,000 miles). At something well over 400,000 miles it finally starting making an horendous noise one day. Turned out the thrust bearings on the crank shaft were worn about 3/8". You could move (push and pull) the crankshaft forwards and backwards by hand about 3/8". The harmonic balancer and some internal parts were starting to hit side wall parts of the engine, but it still ran, and it still did not burn oil and I was running straight 40 weight dyno oil in it. (plus some oil additives).

 

[Boxil]

heres some new update on my 88 knock at idle. i've got the valve cover off and took out the rods and the rockers, nothing noticeably damaged that i can see. the rods are kinda interesting. they are bare metal on the lower half and a kinda blackish almost burnt on oil or something. not sure what it could be. dont know if it has any effect on the knock/tick at all. since i dont see anything wrong with those parts i will prolly put them back in. took out the plugs and the arms are pretty fouled up. kind of a coated on char. but its a whitish color. will be replacing those. other then that cant think of anything else until i can get the oil pan off and look from ther. oh yeah most of the rods i could spin in ther holes except for like 2 or 3 of them. they were tight. (maybe just tension from the lifters?) well any ideas or thoughts would be great. thanks alot! :dunno:

 

[fender]

The pushrods will be tight when the cam is pushing on them. They should spin when the valves are completely seated. I doubt the pushrods or the rocker arms have much to do with the tick... but the tappets/lifters on the bottom of the pushrods might.