knocking engine sounds.

aro · Mar 25, 2006

Hi guys, I am new at this forum, btw my name is Stanley, I live in Indoneisa and I have 1997 Cherokee XJ which in the US is equivalent with the 1995 Cherokee XJ limited. I bought this cherokee not long ago, and I am having this problem regarding a strange knocking or ticking engine sounds at idle RPM in neutral. It seems that the knocking sound is coming out from underneath the engine, it is even more obvious if you go underneath the car, but the noise goes away rite away when I rev up the engine to abt maybe 2000 rpm. I used to think that maybe the noise came from the tappet (lifter), so I decided to replace them with the new ones, I used crowns instead of mopar. Does the utilisation of non mopar parts become the reason why the knocking or the ticking sound still exist? I talked to my mechanic 2 days ago, and they told me that it was quite normal for a cherokee to have that particular sound. But i don't really trust them. Is this true? and what is the normal oil preasure indicator that this car should show at the oil preasure gauge at idle when it is cold and warm, and when it accelerate under both warm and cold engine temperature condition., I am using 10-40 mobil 1s oil at the present time. and usually at the oil preasure gauge at idle when it;s cold the needle stay at the center which is the 3rd needle from the left, and it drops a little bit higher than the second needle from the left when the engine is warm, but it will raise up to the 3rd or maybe slightly to the right of the 3rd needle when I rev up the engine. is that normal? I hope somebody on this forum can give me some information regarding the abnormalities that I am experiencing. thanks

XJHummerRescue · Mar 26, 2006

My '89 has had rocker arm ticking and tapping since I bought it, quieted down after I switched to synthetic, but I figure it's normal, since all of my buddies Jeeps do it (6 Cherokees and 1 Wagoneer). Oil pressure went up after changing to synth. too, so mine may not be normal, but oil pressure cold is around 55 psi, 35 psi warm, and varies while driving (usually 50-65 depending on engine load and speed).

carnuck · Mar 26, 2006

They do tend to have piston slap noises. I made mine mostly go away with a can of Engine Restore.

Dr. Dyno · Mar 26, 2006

aro said:
Hi guys, I am new at this forum, btw my name is Stanley, I live in Indoneisa and I have 1997 Cherokee XJ which in the US is equivalent with the 1995 Cherokee XJ limited. I bought this cherokee not long ago, and I am having this problem regarding a strange knocking or ticking engine sounds at idle RPM in neutral. It seems that the knocking sound is coming out from underneath the engine, it is even more obvious if you go underneath the car, but the noise goes away rite away when I rev up the engine to abt maybe 2000 rpm. I used to think that maybe the noise came from the tappet (lifter), so I decided to replace them with the new ones, I used crowns instead of mopar. Does the utilisation of non mopar parts become the reason why the knocking or the ticking sound still exist? I talked to my mechanic 2 days ago, and they told me that it was quite normal for a cherokee to have that particular sound. But i don't really trust them. Is this true? and what is the normal oil preasure indicator that this car should show at the oil preasure gauge at idle when it is cold and warm, and when it accelerate under both warm and cold engine temperature condition., I am using 10-40 mobil 1s oil at the present time. and usually at the oil preasure gauge at idle when it;s cold the needle stay at the center which is the 3rd needle from the left, and it drops a little bit higher than the second needle from the left when the engine is warm, but it will raise up to the 3rd or maybe slightly to the right of the 3rd needle when I rev up the engine. is that normal? I hope somebody on this forum can give me some information regarding the abnormalities that I am experiencing. thanks

The oil pressures are normal so the good news is that the rod/main/cam bearings should be in good shape.
Most 4.0 engines will make a soft ticking noise at idle when cold and that's normal piston slap. A slightly harder-edged metallic ticking sound is usually a lifter or a rocker.
Your noise is coming from underneath so it could be something different. Since your model is a Limited, I'll assume you have an auto tranny so it's possible you have loose flexplate bolts. Ask a mechanic to remove the bellhousing inspection cover to inspect.

knocking engine sounds.

aro

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XJHummerRescue

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carnuck

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Dr. Dyno

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