93 4.0L sounds like a diesel - JeepForum.com

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post #1 of 28 Old 04-19-2010, 03:07 PM Thread Starter
dudeinajp
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93 4.0L sounds like a diesel

I'm just curious if this is normal. The PO says the bottom was rebuilt w/ new oil pump about 10k ago, 110,700 on it now. He did it because of the gauge reading low and inconsistent and not being familiar with the 4.0L. It was reading the same after the rebuild as well. Changed out the sender, same. He put a mechanical gauge and it was reading good and steady oil pressure. I want to know if all is okay and not have to worry about it. I've had other 4.0L Jeeps, but none sounded like this one. It runs great though.

Here are a couple of vids.





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post #2 of 28 Old 04-19-2010, 05:59 PM
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Almost sounds like piston slap to me. The reason I dont think it is rod knock is when you revved it the noise went away. Usually rod knock will get louder and louder with more revs (just went through this with a Neon I had). Its a bit hard to tell from the audio but that is my thought. Take a long screwdriver and place the handle into your ear and touch the metal end around to various spots on the block. Use it as a stethescope. Its the quickest and easiest way to figure out where the noise is coming from.

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post #3 of 28 Old 04-19-2010, 06:10 PM
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Its the lifters. My g pas wrangler is the same way. They most likely are gummed up and dirty. The right way to fix em is to replace em. But you can run half a qaurt of atf ( yes I said atf) or marvel mystery oil to clean em up. The atf is high in detergents and will help clean em up. You would be suprised the diff it makes. You can also use sea foam but I kinda worry bout putting something thin as water in my oil. Run it for a few hundred miles and go easy on it. If ya gonna pull loads or hills AI would put fresh oil in first
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post #4 of 28 Old 04-19-2010, 06:33 PM
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i heard that SeaFoam is supposed to help sticky lifters... i used it in my jeep and it seems to be running smoother.. people told me it helped their sticky lifters so if it is the lifters then maybe this will help. just search seafoam how to on youtube maybe even add in jeep to the search and you will see what i mean..
Any questions PM me and ill try to help as far as sea foam goes.
Good luck! later

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post #5 of 28 Old 04-19-2010, 06:45 PM
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I have done the sea foam in the intake. Make sure ya have a breezy day lol! It makes some smoke
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post #6 of 28 Old 04-19-2010, 07:41 PM Thread Starter
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Originally Posted by 1stockjeep View Post
Its the lifters. My g pas wrangler is the same way. They most likely are gummed up and dirty. The right way to fix em is to replace em. But you can run half a qaurt of atf ( yes I said atf) or marvel mystery oil to clean em up. The atf is high in detergents and will help clean em up. You would be suprised the diff it makes. You can also use sea foam but I kinda worry bout putting something thin as water in my oil. Run it for a few hundred miles and go easy on it. If ya gonna pull loads or hills AI would put fresh oil in first
I'll give this a shot. I just changed the oil w/ some 15w40. If it doesn't work, I'll just have the head I have rebuilt before I pull the old one to replace the lifters and I assume the cam as well. The exhaust manifold needs replacing too, cracked, so I'll just do it all at once. As long as it will get me through until next spring, I'll deal with the noise.
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post #7 of 28 Old 04-19-2010, 07:46 PM
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Welcome to my world. Mine sounds just like yours and has been sounding like that for years. I'm at 296k miles but it runs great. A little noisy but I can't justify tearing it down when it runs so good. I've tried thicker oil and mystery marvel. Nothing helped.

Me and my buddy just replaced the cam, lifters, timing chain, and had a valve job done on his 258 4.2L and it's so quiet. I was jealous.

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post #8 of 28 Old 04-19-2010, 07:55 PM Thread Starter
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Originally Posted by Louie4 View Post
Welcome to my world. Mine sounds just like yours and has been sounding like that for years. I'm at 296k miles but it runs great. A little noisy but I can't justify tearing it down when it runs so good. I've tried thicker oil and mystery marvel. Nothing helped.

Me and my buddy just replaced the cam, lifters, timing chain, and had a valve job done on his 258 4.2L and it's so quiet. I was jealous.
That's why I tried the 15w40 oil and it didn't do anything. The MMO may not either, but it's worth a shot.
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post #9 of 28 Old 04-19-2010, 08:21 PM
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The thicker oil may not help because the lifter is plugged and the oil cant get in. I ahve seen these things run for long time makin all kinds of noise! Buy a loud stereo. Thats what i did
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post #10 of 28 Old 04-19-2010, 08:36 PM
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That's why I tried the 15w40 oil and it didn't do anything. The MMO may not either, but it's worth a shot.
$4 for the MMO. Definitely worth a shot. I try to use it every other oil change. As a matter of fact I put the larger oil filter on and increase the oil capacity a little.

Lou

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post #11 of 28 Old 04-19-2010, 08:39 PM Thread Starter
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Originally Posted by 1stockjeep View Post
The thicker oil may not help because the lifter is plugged and the oil cant get in. I ahve seen these things run for long time makin all kinds of noise! Buy a loud stereo. Thats what i did
I turn the stereo up too.

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$4 for the MMO. Definitely worth a shot. I try to use it every other oil change. As a matter of fact I put the larger oil filter on and increase the oil capacity a little.
I didn't think of using a larger filter. I'll have to remember it for next time.
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post #12 of 28 Old 04-19-2010, 08:47 PM
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I didn't think of using a larger filter. I'll have to remember it for next time.
At Autozone it was right next to the STP S16 filter (one called for in the book). I think its an S8. I don't know how much it really did for me but it didn't hurt.

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post #13 of 28 Old 04-19-2010, 08:59 PM
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Sound's like Jimi Hendrix to me

I'd say lifters, when I changed mine it made that sound (except only once lifter was hitting). I just took the valve cover off and ground down where it was hitting to give it a hair of extra clearance. I'd recommend changing them before you go that route though.

Also, good pick on getting the YJ

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post #14 of 28 Old 04-19-2010, 09:14 PM Thread Starter
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Originally Posted by omarambo101 View Post
Sound's like Jimi Hendrix to me

I'd say lifters, when I changed mine it made that sound (except only once lifter was hitting). I just took the valve cover off and ground down where it was hitting to give it a hair of extra clearance. I'd recommend changing them before you go that route though.

Also, good pick on getting the YJ
I have an extra block and head that came with the Jeep, he was going to build a Stroker. I think I'll do the same. A budget 4.5L since the funds are and will be tight.

Thanks. I love the YJ. It's much more fun than any of my previous XJs or the ZJ I sold to buy it.
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post #15 of 28 Old 04-20-2010, 09:17 PM Thread Starter
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After closer inspection. The sound is at its loudest where the engine/transmission come together. I'm going to change the fluid in the transmission to see what happens.
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