WEll thats not what my xjs are doing.. I am going to guess you have a piston skirt thats going or cracked.. Seems like that happens to a lot of grand cherokees around my area.. the noise you have explained sounds like it... Just my thoughts..

 

Uggh 00XJ I hope not....at least it is intermittant now so maybe it's not about to let go.Does anyone on her know how I could tell for sure what is going on?short of pulling the head and oil pan off that is.I am hoping for a lifter or valve problem, not a cracked skirt...but either way it would be good to know...

 

since i have changed my plugs and gave it a tune up mine doesnt do it as bad. the po had two different types of plugs in it and they where both the wrong kind.

 

Another thing i would reccomend is a whole can of marvel mystery oil in the crankcase...The noise also sounds like your not getting oil to a lifter or valve...This is what i am hoping will work for you and the only thing i can think of that would be happening. maybe when you changed your oil you blocked the oil supply to somthing..?YOu could do a compression check and see if you cylinders are all reading good, its not going to give you any answer to your noise though.. Its really hard to say what your noise is because it happpens on and off and only on a start up... right...???? get some mystery oil and see what happens, i wish you luck.!!!,glen

 

another thing i noticed when doing the head gasket on my 93 country. When i first got the jeep it had a blown head gasket.. I started it up to see if it would run ..The jeep had a BAD knock for about 20 seconds after start up, very loud like you have explained......turns out the jeep had BAD scored marks on the top of the pistons surface...The p/o had the wrong plugs in and the pistons were hitting the spark plugs...Just my thoughts.... try new plugs..! WE are all here to help....

 

sounds like a collapsed lifter.. I would try some seafoam or MMO and see if that get it freed up and then some oil may stay in there...

another thing to try is putting in some "engine restorer" or Lucas" this doesn't always work but it may keep some lube into the lifter so when it is started up cold it wont clamp so loud

 

It certainly sounds like a lifter that is draining down. They can be quite loud at the beginning if they are totally dry. With the 4.0l's extra long turn over time.. you can crank it over a few times, before trying to start it to get the oil pump turning...

What kind of oil are you using?? If you are using something with a heavy paraffin base stock like Penzoil, Q-state, or their no name brands. Then you could be experiencing sludge related issues.

Avoid oil thickening agents like Lucas, or Restore. These are going to make your issue worse not better. You don't need a thicker oil, you need it to flow quicker.

Marvel's Mystery Oil is really nothing more than Kerosene and a couple of esters. In this case MMO might actually do some good. If you do have sludge issues MMO will help clean that out. Using a better grade of oil would help also...

Open your oil fill cap.. Look inside at the rocker arms, what do they look like? Are they dark colored with obvious oil coverage. Or is the covering a lighter amber color?

One more good way to clean out any crud, dirt and sludge in your motor. Drain your oil..put on a cheap filter(the ONLY good use of Fram orange) Pour in a gallon of diesel. Start the engine up and let it run about 10 minutes. The diesel has enough lubricity to protect the motor at idle, plus any residual oil left inside the motor will help. Drain the diesel and replace the filter with something good. Napa Gold, Wix, Purolator Pure One, Mobil 1, Mann, Baldwin are all good filters for the 4.0l. Put in 6 quarts of oil. And see how she sounds. When you drain the diesel... its should be very black and quite nasty. That is all crap out of the inside of your oil galleries.

 

Very good info here ... DO as he says and IF the problem continues THEN be worried..

 

Ok folks here we go....First off thanks to all who replied,sorry I could not get back to here till now I spent the ENTIRE day in traffic back from Orlando. So this morning go out,its was 18 degrees last night and was only 24 this AM,start it up and the worst racket ever I am thinking this is bad. So a little more background...I always run Valvoline premium 10w-30 with a Napa Gold every 3,000, no sludge visible,never been run hot, loses no oil and no coolant,so needless to say I'm feeling lousy about this thing being about to explode right? So since it is SOOO loud this AM I figure what the heck I will pop the hood and listen again to see if I can isolate it....and low and behold, I see this little cylinder thing on the right of the TB,mounted on the fender,trying to rock itself right off its mount.Put my ear to it...it's tapping inside.LOUD.It has two vacuum lines and an electrical connector. Pull the connector....and whisper quiet. This threw a CEL,so I plugged in the Actron...EVAP purge valve fault. Jsut to be safe changed the oil to 5w-30.Let it cool all the way down,fired it up,not a hint of a noise. I think that has been the problem all along.Can't believe I didn't hear that thing the first time. In any case I hope this may help someone who may have the same issue, I guess that thing has a little piston in it or something. Glad it seems to be nothing internal,I will post if any noise returns.Thanks again!

 

do yuo have any pics of the thing that was making the noise

 

very glad you found your dreaded noise!!!! I would like to know what your talking about though..? seems to me like a abs unit or pump or somthing..??? I have no idea, i dont know what would make a noise like that by the t/b.. let us all know with pics and stuff, and again VEry pleased with you getting this solved...

 

will try to post pics, it appears to be a system to reduce emmisions via pumping spent gasses from the exhaust manifold,and also the fuel tank? At least thats where the lines go...now ot see if I can make the camera and the internet play nice...

 

Ok I cannot for the life of me get these pics to post,but here is a link to a Pic of the part. I just unplugged it until I can go pick up the new one, threw a CEL but no other http://www.autozone.com/autozone/cat...purge+soleniod

 

ok well i have been doing oil changes for 5 years at this little shop, and the inline 6 grand cherokees DO take 6 quarts of oil, and usuaully when you change the oil in any car, the first time you start it up after the oil change, it will more than likely sound like you dropped a bag of rocks in the motor, but usually it only last less than 5 seconds, i know this isnt your case, but its possible that you might not be getting oil pressure even though your "crappy" stock oil pressure guage reads good...just a possability

 

ooo i didnt read the part where you found out what it was haha, its always the smallest things