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Unread 01-08-2012, 11:14 PM   #1
tcope0094
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Cherokee rough idle

I have a 97 Cherokee sport 4.0 and I am not entirely sure what is wrong with it. I should start by saying that I dont really drive it that much, only when it rains because I have a motorcycle that gets about triple the MPG. But since I hadnt been driving it that much I never put antifreeze in it when it started getting cold, i just kept regular water in it and a pretty bad cold spell swept through and the water froze and my dad was driving to a friends house when he said it started smoking and busted the lower radiator hose and quit on him. So he put on the hose and drove it home and we ran water through until all the air was out of the lines then put water and antifreeze in it but now it idles very rough, like shaking the jeep rough. And when the engines cold it will start right up but if i crank it and let it warm up then try to crank it again it doesnt want to start. Also when i come to a stop the revs shoot down to about 100-200 and it almost stalls. Also the heat doesnt work very well. About a year and a half ago i cracked the head on it and had to install a refurbished one and it was a pain to tear that engine down and im thinking maybe its a messed up valve or something or a broken vacuum line somewhere. Id really rather not rip the engine apart to find out it wasnt the head or valves or block. it sounds like a vacuum line to me but i wanted another opinion. Anyone have any thoughts?

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Unread 01-09-2012, 04:54 AM   #2
tjwalker
It's the crank sensor!
 
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The fact that the engine was partially frozen, the subsequent overheat and now you have driveability symptoms is most likely not a coincidence.

You most likely have some engine damage here. If you're lucky, you had an overheat because of a frozen cooling system and it blew your head gasket or cracked your head. Cross your fingers that the block is okay.

Irregardless, it is time for some testing. Start with a simple compression test.

Spec for the 4.0 is 120-150 psi, with no more than a 30 psi variation between cylinders.

And as you know now, I would never leave plain water in your XJ. 50-50 is a good mix for the majority of people's applications.
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Unread 01-09-2012, 08:19 AM   #3
tcope0094
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Yeah its a cracked block, saw it this morning. Water coming out just behind the water pump, thought it might be the weephole but I saw the crack. Then I decided to frive it anyway and now im on the side of the road overheated. Not a good choice. Would some jb weld fix it temporarily? And is there anyway to permanently weld it?
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Unread 01-09-2012, 08:38 AM   #4
tjwalker
It's the crank sensor!
 
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Quote:
Originally Posted by tcope0094 View Post
Yeah its a cracked block, saw it this morning. Water coming out just behind the water pump, thought it might be the weephole but I saw the crack. Then I decided to frive it anyway and now im on the side of the road overheated. Not a good choice. Would some jb weld fix it temporarily? And is there anyway to permanently weld it?
You could perform a close inspection of the block to see what size/kind of a crack it is and if it can be welded. JB weld is not a great answer, but if the crack is cleaned properly, you might be able to get JB to seal it. For how long though is the question.

But I think I'd also start shopping for a salvage yard replacement engine, as you likely have cylinder head problems too besides your cracked block. You may want to make this engine a boat anchor.
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