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'91 I6 4.0 4X4 engine knock, increases with RPM's

DrRandy

NAXJA Forum User
Location
B'Ham Alabama
175,ooo miles, $500:cheers:
oil was VERY black till i changed it AFTER this problem, changed to 20W 50

ok... got the jeep a month or so ago. ran fine till this... on interstate and went from no ac/heat to "vent". XJ died shifted to "N" slowed down to like 30mph or so then finally started back up. Engine now "knocks". Much louder when i first start it up. Then seems to settle out to a loud tick more than a knock as the engine heats up??? The knock/tick does increase in speed of knocks/ticks as the RPM's go up.
Also, when i turn on the heat the belt screames for a few seconds if i'm at idle. dont know if it's related? in fact dont know if the first time i went to vent is related. Just using the cause/effect mode to diag. the problem.
Any suggestions?
*O ya sounds to me like the knock is coming from the top of the engine
Have driven close to 100 miles or so with nothing getting worse.
Engine still as great power and "get up", no smoke, smells, etc
oil pressure is good..i think... little over 1/2 way (i think 40 is half?)

sorry for the long post, trying to give all details!!
 
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anyone??
 
you say the engine has the same amount of power? I had a push rod break in two jeep 4.0 on the front cylinder. I would pull the valve cover, start the engine and make sure everything is okay there. It will squirt oil through the push rods but it is not that bad!
 
Thanks guys, Yes Automatic trany. I say plenty of power, this has more "get up" than my DD which is a 2006 with only a hand full of miles. I guess what i'm getting at is the engine dosent seem to affected by the knock, YET!

I've read the forums and it seems that the TC bolts and flexplate issues have the knocking from the rear/underside of the engine?? This i'm about 85-90% sure it's coming from the lifter/valve cover area. Would a stethoscope help pinpoint pretty close...never used one.
thanks
 
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A stethoscope might help, but having just gone through this, it even sounds like the same noise. Mine started doing it immediately after I swapped the intake manifold. They were completely unrelated, but it definitely made me look around the intake area for quite awhile before I finally got underneath and checked the TC bolts.

Jim www.yuccaman.com
 
Will do it guys thanks! I'm out of town till Tues but will do it then and post results
 
Checked the TC bolts yesterday. All tight and fine:( Guess i'll just keep looking and ripping apart everything. Next is the valve cover
Thanks again
 
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