anthony001

when its idling its fine but when i get it up to 4k rpms it starts knocking or ticking then go's away when it changes gears.pistons worn maybe???

89Laredo

Maybe detonation?

firstime00XJ

either detonation or for some reason at higher RPMs the oil isn't getting pumped into the valve train and he's getting lifter tick. If it was a piston, it would almost seem to do it all the time. Pull your plugs and see what they look like. Where's your oil pressure at when you're running 4,000 RPMs?

anthony001

When I changed the plugs the back one was the worst it had crud and oil on it. I think it's what u said about the oil not being pumped. The pressure is probably at half and it burns oil quicker but no leaks. Every now and then I have to add a quart. Idk what it is

89Laredo

sounds like time for a rebuild if its burning oil..
or at least new pistons/rings.

firstime00XJ

Yeah sounds like ring failure...hopefully you're not experiencing piston slap and it is the valvetrane. If you've got the money or the mechanical ability, I would pull the head and take a look at it and the pistons. Keep us udpated!

spyder9x

I don't understand why guys that own jeeps worry about lifts and tires and stuff first thing but don't put an oil pressure gauge on there..they cost like 15$, if it didn't come with one from the factory. "The pressure is probably at half" doesn't tell me much. 5 minute bolt-on affair. Rather than pull the head and all that fun stuff, get a PSI reading and let us know.

anthony001

stock guage reads 60 at 3k rpms..the noise goes away once i add oil but idk what it is the guy i bought it from said that his mechanic rebuilt the block..i wonder if that was total b.s?/??

spyder9x

When checking oil pressure, it should be done at idle and with the engine hot. Revving the engine causes the oil pump to spin faster and will give wild readings. Both my jeeps would show 60-80psi at 3k RPM. At idle my 94 gives about 40 and the 99 gives 60psi.

fishtaconc

Could be quite true that lower end was rebuilt.... he could have just had bearings installed, maybe the cylinders wernt honed properly or at all.