We have a 1997 Jeep Cherokee 4.0 and a few months ago(i dont drive it much) I noticed a spark knock, rattle, ping, whatnot while pulling hills under certain throttle. I told her to start using a different gas...and she has BP. Well the other day I noticed it again, so i dont believe its poor gas quality related.

It has 91,000 on it, and I have done everything tune up and service wise. I worked for Ford and over the years there was a few TSB's here and there about advanced timing for spark knock, etc. Just wonder if anyone has Jeep experience.

Thanks

 

I think that's just a common Jeep thing with the 4.0L. My wife had a 99 with about 65K on it and it did something similar and was never able to find out what it was so we just traded it in. Sorry I couldn't solve the problem for ya!!
Good luck!

~Nick

 

Yup, its just a Jeep thing. Don't worry about it unless you lose oil pressure. I was a jeep tech, and my business specialized in Jeeps. There are several things it could be...I listed several in another similar thread on this forum. First, the timing isn't adjustable on that engine, so don't bother with that. 4.0s are notorious for "piston slap", even on low mileage motors. Nothing to worry about...its common and isn't a problem. Many also have a very slight lifter tick at idle, and I have seen several owner's get told they needed new engines because of either of those things (or both). My buddy bought a Cherokee for $200 because a Midas shop told the woman who owned it that it needed a new engine, so she put it up for sale cheap. My buddy hasn't done a thing to it...and that was 3 years and 50,000+ miles ago.

Anyway...just run it. Your engine is a 40 year old design dating back to the old American Motors days, and the original motors were used in such cars as the Rambler. American Motors and Jeep joined forces, and Jeep used the 232 and 258 I-6 engines in their vehicles. Before Chrysler took them over, AMC modified the engine slightly (reduced the stroke and increased the bore) to go from 258 to 242 cubic inches, and added fuel injection. In 1987 (the first year Chrysler owned AMC), the 4.0 (242) came out in the Cherokee. The head and fuel system was redesigned for 1991, adding power, and the engine started to be used in Wranglers the same year.

Sorry for the history lesson...the point I was making is that the engine is tried and tested, and because of the old design, its a bit noisier than more modern engines. But because of the simple, time tested technology, they are known for easily lasting 200K+ miles. i had one that was still running great at 332,000 miles, but I finally retired the Jeep because of rust. From what I could tell, the engine had never been apart.

Jim

 

Yeah ours ran great still, I just got tired of the noise and plus we wanted something bigger............but I can honestly say I never had any problems with it other than that noise