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Discussion Starter #1
My '98 stock XJ is running rough. Like, sad go-cart rough.

The Problem: The engine has very little power, is slow to accelerate, has a 'puttering' sound like a go-cart, and smells like poorly burned gas.

Steps I've taken so far: Replaced - Distributor, spark plugs, spar plug wires, both O2 sensors, and the idle air control, as well as fresh oil, oil filter, and air filter.

There has been a slight improvement in the way it idles (a bit less rough now). Holding my hand over the exhaust, I feel an obvious puffing of air. Seemed like prior to all this, the exhaust was more of a steady stream of air pressure. Should I give up and take it to a shop, or is there something obvious in my description that points to another problem?
 

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How many miles? Have you run a combustion chamber cleaner or fuel injection cleaner through it? How old are the fuel and air filters? Any vacuum leaks?
 

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Discussion Starter #3
How many miles? Have you run a combustion chamber cleaner or fuel injection cleaner through it? How old are the fuel and air filters? Any vacuum leaks?
Gluckmysock, the jeep has 212k miles on it. I ran some basic fuel cleaner through it a couple times. The fuel filter hasn't been replaced since I purchased the vehicle over 6 years ago. Air filter is brand new. I'm not sure how to check for vacuum leaks.
 

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  1. As far as the mileage it's nothing to worry about for these engines. It just helps us focus our efforts. The fuel filter is in the tank and has to be dropped. It's not really a filter but a sock that a attaches to the fuel pump.
  2. The vacuum lines should have a diagram on the firewall. It's pretty much all the air hoses hooked to your engine. One even goes clear back to your fuel tank. Small leaks can cause your engine to run rough, stumble and even stall. Garages use a smoke machine to help look for leaks. You can just start tracing them from one end to the other and look for cracks or brittleness. If it looks questionable, replace it. Vacuum line is cheap. Don't let a parts store sell you fuel injection hose. It's way more expensive. If your fuel tank vent hose needs replaced, get some rated for gas, but it don't have to be fuel injection.
  3. Check your wiring harness that goes around the back of your engine, it can rub through and short out.
Good luck.
 

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Discussion Starter #5
I had a mechanic out to diagnose the problem. Turns out that I have two cylinders with no compression. He said at the very least I have a blown head gasket. And it might need to have the whole head rebuilt or replaced. He thinks that you should probably get rid of it before it costs a ton of money.

I've been able to perform 99% of the work on it so far. Would I be getting myself in over my head by taking on a head rebuild?
 

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A head gasket is not a difficult job. You have to take your time, clean and torque everything properly, plan on broken/Stubborn bolts. And it taking longer than you expected. Guys have done it in their driveway in a day, but have a lot a mechanical experience. You will need new head bolts.
 

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Discussion Starter #7
Pulled the head. The head gasket is completely burned through between the 5th and 6th cylinders. I’m guessing this explains why cylinder #5 has no compression. I don’t see any obvious tears or burns around cylinder #1 (the other cylinder with no compression). However, there is a LOT of carbon buildup everywhere. Also, the gasket has these crazy caramel brown deposits in some of the holes. I tried to capture everything with the camera.

Will this much carbon lead to no compression? Also, what are the best practices for removing carbon? I don’t want to damage anything.
226900
226901
226902
226903
 

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Discussion Starter #8
I found a shop that will clean, test, resurface and re-seal all the valves for $200 using the original springs and valves. Or, I could buy a remanufactured head with all new springs, valves, etc for $375. If this was your jeep, which option would you choose?
 

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How many miles on that head? Will that shop rebuild it, or do they just clean and test it? I would be cautious about a reman, what quality are the valves and springs?
 

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Discussion Starter #10
Gluckmysock, I believe it is the original head and the engine has 212k miles on it. The shop reported that the head has a crack, so that's toast. If the head has a crack, should I worry about the rest of the block? I would hate to buy a new head only to discover that the rest of the block is no good.

I found a company called Gearheads that claims their reman heads have all OE parts or better.
 

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Its rare that the block is cracked Its usually the heads. Check out some reviews. I have heard of gearheads, but don't know anything about them.
 

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Following along to see what you discover next. Also for self motivation. But keep us updated on what you decide. I recently was reading about a build where the guy bought a crap reman head, and fought for a refund, then had a much better experience with a Clearwater brand head. I think TLC (something like that) was the bad brand.
 

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Discussion Starter #13
Update. I bought a remanufactured head from Gearheads. My experience with them was good. Head looked brand new. Bought new head gasket, head bolts, head cover gasket, and reinstalled everything. It started on the first try and drove like a dream. It had power like I never remembered. I was happy.

Days later, it took a sudden turn for the worse. Suddenly, it lost almost all power. The engine shook violently and there was a really loud knock coming from within the engine. After some research, my best estimate is that I have at least one spun bearing. :cry:
 

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Just hunt down a cheap 4.0 engine! I got really lucky one year and snagged a 4.0 with only 76k for $250!
It was at Pick n Pull during a half off sale.
And the only damage was a minor fire from a fuel rail leak... hahaha.
 

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Discussion Starter #15
Nice!

I found a shop in Colorado that specializes in rebuilding the Jeep 4.0. Almost all the internal components are replaced with new parts. It has a 1 year warranty. They are also gonna do the install, which also comes with a 1 year warranty. It's more expensive than a Pick n Pull engine, but I figure it will add another 150k-250k miles on to the life of the rig.
 
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