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Discussion Starter · #1 ·
Hi, I'm a newbee to this board. I have a 1993 4.0 automatic with 150k that has a constant ticking sound during and after warm up and at all times sounds like a diesel motor (I had a guy say to me "I didn't know they made a diesel wrangler" I replied "They don't"). Smoke comes out of the tailpipe under hard throttle. I don't know the color yet, but it smells like it has too much fuel in the mixture. I recently changed all the spark plugs and found that there were signs that they all had been used way past their service life. Also, during recent fill ups I did the math and found that 13.5 mpg is the average (my gas gauge doesn't work). Any help would be great.
 

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Think about getting a Major Tune up with a Valve adjustment. At the least, Valve Adj.
If that doesn't cure your issue, then I'd think about looking at the Lifters & Cam / Valves.
What your describing sounds exactly like Lifter Noise, and the above would be causes
for that. (unless your really low on Oil, or Oil Pressure)
Be sure to have a Compression check performed as well. Your Motor could very well be
Tired and in need of a Rebuild. Most 4.0's will exceed 200,000 miles before that is
needed, BUT that depends on how it's been driven and maintained. If the previous
Owner drove the Sh*t out of it, or you have, or not maintained properly, well then, that
would be a good reason for it.
The Smoke could be caused by the Valves, Rings, or even Carburetion. Again, that's where
a Major Tune up would help determine the extent of your issues.
 

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Discussion Starter · #3 ·
I just had an oil change and it doesn't look like it's leaking anything.
 

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Could be too many of things.

First I'd check the compression.

Just go to YouTube to learn bow to check compresion

That's where I'd start.

The guy who posted before me was right on
 

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I just had an oil change and it doesn't look like it's leaking anything.
Hows the Oil Pressure ?
At Idle ?
At 2,000 RPM ?
 

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Also, how long have you owned the Jeep, and has this been going on since you got it?
 

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Discussion Starter · #7 ·
I bought it four days ago and it ran like that since I bought it. The oil pressure at idle is about 36 to 38 and I don't know what it's like at 2000. I'll take a look at it sometime tomorrow.

P.S.
I forgot to say this before. I smells like there's too much fuel in the mixture at all rpm's.
 

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At 30 psi at Idle your Oil pump should be OK. If your smelling Gas, the Carb may need adjusting or rebuild. But get a Compression check performed, it will help narrow down your issues, whether you need a rebuild on the motor or not. But at any rate, you have lifter noise,and that needs to be checked to determine exactly what the cause is.
 

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most 4.0s always have a certain amount of mild lifter tick

but you may have an exhaust leak or bad O2 sensor if it is running rich
 

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piston slap

I know with my old 94 4.0 YJ there was a piston slap issue that Chrysler was aware of, it sounded a lot like a Diesel. I don't remember exactly when my Jeep developed this issue but Chrysler was offering to swap in a new short block or extend the powertrain warranty. I went with the extended warranty as I didn't want the dealer tearing my Jeep apart. I sold the Jeep at 100k miles and it ran perfectly fine. Maybe this has something to do with your issue.
 

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I have seen/heard quite a few 4.0's sound like what you are describing. My bet is the valve train making the noise. It really isn't that bad of a job to do. Most decent shops can do it for probably under $300.00 I would think. It takes more time than anything else. And a valve cover gasket.
 

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I thought they were hydraulic lifters? Min's doing just as described, oil pressure is 45 or so? So are the rockers adjustable??
 
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