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Umm what does it mean?

S

studstill

NAXJA Forum User
Location
Layton Utah
Ok i got my xj 2 weeks ago 250000 miles on a 91 4.0. Started with a little click coming from the motor. Went and started it today to keep the battery charged. The click was a lot louder then a click it was more of a knock untill the motor starts to warm up. Also there is smoke coming out of the oil level check tube. the exhaust feels like there is a miss but the motor runs ok doesn't shake like its missing. what does it mean?
 
Give it a good oil change and see if it looks milky or anything to see if maybe the head gasket is worn or something. When changing the oil I and alot of us here will recommend some lucas or MMO be added to help out.
 
Well, given the mileage I'd probably start off with a compression test of all cylinders. Inspect the plugs while they're out, replace if necessary, and not with E3's. Give the cap and rotor a look-see. That should be enough to give a basic idea of the mechanical state of the engine.

That's just me though..
 
I would second that I would highly doubt that if you do have a serious knock issue that an oil change would be the solution.

That said its always good to change all fluids following the purchase of a new to you jeep. While you are doing that make sure said oil isnt milky white.
 
Well im going to change the oil. The guy i bought it from did a tune up a month before he sold it or so he says. cap looks new wires look new. but i will let you know if just the oil change doesnt fix it. but i appreciate all your posts.
 
Probably a dumb question, but have you checked the actual level of the oil?

As mentioned, the only way to verify what shape the motor is in is to do some basic diagnosis (check condition of plugs, get a compression tester and check the compression of each cylinder etc etc). Even though the 4.0 is quite the stout motor, at 250K with "knocking" and "smoke from the dip stick tube", you might not like the results you see with your diagnosis.
 
As said, a compression test and a vacuum test while running will tell you a lot about the condition of the engine.

Check the CCV system for clogging.

Use a good quality oil filter with a silicone anti-drain back valve--the cheap Fram filters have a crappy nitrile rubber valve and that is not good on bottom-up vertical or horizontal mounted oil filters.

Use a good quality motor oil--I recommend Shell Rotella 10w30, the dino version can be found for about $8 a gallon at Walmart around here. Diesel motor oils contain ZDDP which is good for flat tappet engines like the 4.0, and it is highly detergent and will clean the crap out of the inside of the engine.
 
Was the jeep inactive for awhile?
The reason I ask, is because I left a vehicle sit for a couple weeks while on vacation. Upon returning and starting the engine, it had a tapping sound that turned out to be a valve lifter, that quieted down after a few days of regular driving. I can recognise noisy lifters from my hot-rod days of the 70's. I put a little liquid wrench in the crankcase, and ran it for about 100 miles, then changed the oil. Noise eventually dissappeared, but would be louder on days when it had not been driven the day before.
Not to hijack, but................
Joe, what is zddp. I am actually interested in running diesel oil. Do you run this all the time, or just for a good flushing every so often?
 
Well changed the oil. still knocks. i dont know but it is really loud close to the valve cover im gonna tow it to my grandpas where he has a cherry picker and im just gonna pull the motor.
 
Does the speed of the knocking increase with engine speed? If so it could be a really bad exhaust manifold crack causing a loud exhaust leak.
 
yes it does i imagine it is either a exhaust lifter or valve that is making the noise i looked at the rocker arms and push rods all seem fine. Went to the machine shop and got to see some horror story parts. bent valves pistons with valves pressed through them i hope my motor doesnt look that bad
 
Run it till it gets louder, then turn the radio up.LOL Seriously, it might be a sticking lifter or something simple. I thought my 89 4.0 with 375,ooo mi on it had a stuck lifter. Turned out the #6 spark plug was cracked in two, top half came out with the spark
plug boot. I've owned this Jeep since it was brand new and still over look the easy fixes.
 
JJacobs said:
Well, given the mileage I'd probably start off with a compression test of all cylinders. Inspect the plugs while they're out, replace if necessary, and not with E3's. Give the cap and rotor a look-see. That should be enough to give a basic idea of the mechanical state of the engine.

That's just me though..
Click to expand...

What's the deal on E3s?
 
my2monkeys said:
Run it till it gets louder, then turn the radio up.LOL Seriously, it might be a sticking lifter or something simple. I thought my 89 4.0 with 375,ooo mi on it had a stuck lifter. Turned out the #6 spark plug was cracked in two, top half came out with the spark
plug boot. I've owned this Jeep since it was brand new and still over look the easy fixes.
Click to expand...

well normaly i do that but my jeep did not come with a radio
 
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