Yet another misterious Jeep sound

I was sitting at a stop light a couple of months ago and suddenly noticed a rythmic clap...clap...clap...
Tried to locate the sound the same day at home and I think it is coming from underneath the valve cover. Searched here and concluded that my engine has the dreaded sticky valve.
Then the weekend came and after changing the oil, the clapping disappeared...after I changed the oil. Now the oil is getting dirtier (about 3K Mobil1 with Mobil 1 filter) and I started noticing same noise again. It is barely noticeable, but it is there and it will get louder.
Anyone having any thoughts? What should I anticipate?
Thanks
Boris
BTW it is a 99 with 130k. When I got it couple of yrs ago had 117k. I live about five miles from work...

do you have an oil pressure guage? I suspect that you're losing oil pressure, try changing the filter.

87manche said:

do you have an oil pressure guage? I suspect that you're losing oil pressure, try changing the filter.

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I do have an oil pressure gauge and everything seems to be normal, no problems there. Thanks

What brand filter ? I noticed that mobil-1 filters are dissapearing from the shelves and they are no longer orderable, price dropped on the instock ones to $6.99 and I tried to order 10 but none at the warehouse and it showed up as unorderable...
I'm trying a pure-one now in one of our wranglers....

RichP said:

What brand filter ? I noticed that mobil-1 filters are dissapearing from the shelves and they are no longer orderable, price dropped on the instock ones to $6.99 and I tried to order 10 but none at the warehouse and it showed up as unorderable...
I'm trying a pure-one now in one of our wranglers....

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The filter was Mobil1. As I mentioned, it was about two months ago when I changed the oil and the noise stopped, now it is coming back. Where do you get your pure one from?
Thanks

I get my pure-ones at advance auto.

how many miles have you put on it since you changed the oil? if its over 3000 your due anyway. my advice would be to get higher viscosity oil next time, better filter, and get some of that engine oil cleanser that you poor into the head. that should clean it up a bit. just make sure all your oil changes are <3000 miles and that thing'll last forever

Am I right in assuming that this noise does change with engine speed? The reason I mention this is that on a 99 there is a complicated evaporative emissions solenoid setup that pulsates, and makes a noise that sounds just about like a bearing going bad at idle. It just happens to occur at a frequency that is about right for an idling engine, but it doesn't change with speed.

Matthew Currie said:

Am I right in assuming that this noise does change with engine speed? The reason I mention this is that on a 99 there is a complicated evaporative emissions solenoid setup that pulsates, and makes a noise that sounds just about like a bearing going bad at idle. It just happens to occur at a frequency that is about right for an idling engine, but it doesn't change with speed.

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now that's interesting.
I'm glad my 87 is just a simple beast.

I run mobil-1 oil and filters or K&N's but do change them every 3K, most times I also do the oil at 3k but if I'm really pressed I do a filter and add a quart then do a change within a 1K-1.5K additional milage.