Yeah. My 1998 jeep grand cherokee has the 4.0 L6 and it is knocking bad all of a sudden. The knocking has always been there that is expected from the straight six which I don't mind at all. This is different. I can turn my radio up a lot and still hear the knocking. It suddenly started while I was driving down the interstate. I think I'm just going to have to pull the head off and replace about a thousand dollars worth of parts. Oh well though.

 

had exactly same happening to our 98 zj just like you described we eventually had loss of power and the jeep started shaking really bad and stumbled home at 20mph its been sitting there since, the knock was always present and 3 different people told me nothing to worry about its just the valves ticking. its still a project i want to fix when the time is right.

how many miles does your zj have ?

marc

 

Knocking is NOT normal in six cylinder engines...

Auto trans?

 

[QUOTE=Tyrrel Widdicombe;3399265]if you're handy pull the oil pan and look for pieces of piston skirt.

4.0s are notorious for breaking piston skirts. Just finished this job on my 2000 4.0. it's really not as bad as I was expecting.

Best wishes!!

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Has oil and everything? Oil pressure is good?

 

Use a stethoscope to isolate the knock.

 

[QUOTE=williamrobert;3399550]Yeah. Just turned 201,000 miles on my 4.0. Not so notorious for breaking piston skirts I guess.

 

[QUOTE=97grand4.0;3400450]Correct.

 

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