ThE_CaPtaIn

My jeep over heated yesterday pretty bad.... And now it has a rough idle it's an 01 4.0 there is no check engine light... Could a bad head gasket be causing this? This I my DD so I need to get it fixed ASAP!

Spoonman

I would say its a good chance that you have a blown head gasket and cracked head.Pull the plugs and check to see if they are wet, you should be able to look into the cylinders with a flash light to see any coolant.If you cant tell if there is coolant or not in any of the cylinders then a compression test would be a good idea.

ThE_CaPtaIn

What year heads will work on a 2001?

ThE_CaPtaIn

found a rebuilt head with a warrenty but i really dont wanna buy a head if i dont have to... what are the chances i can get away with just changing the head gasket. does any make a MLS style head gasket for the 4.0?

ThE_CaPtaIn

Ok game changer. The rough idle went away when I cranked it up after it sitting over night... So i did a compression check to be sure the head gasket wasn't blown all cylinders had over 120 psi of compression. So I dont think the head gasket is blown.... But since I pulled the plugs I went ahead and changed them. Just used champion coppers nothing special I have read those are the best to use. Well after I got the coil pack back on plugged in I cranked it up and it pretty much went to ***** it will run idle jumps between 200 and 1200 runs very ruff has a flashing check engine light which I assume means it's in limp mode cuz it will not rev over 3k rpm. Can anyone give me an idea of how swapping out plugs to new one can cause this drastic of a result. It was running fine b4 I pulled the plugs todo the compression check. Please help any ideas???

Spoonman

I wouldnt just go out and just buy parts before diagnosis, I was just suggesting that its a good chance the hg is blown or head is cracked.
If the idle is fluctuating between 200 and 1200 r then to me sounds like could be iac problems. I could be wrong and just shooting ideas to you.

ThE_CaPtaIn

Ohh I know Im not I was just trying to get and idea of choices and availability in my area to get my hand on a head if need be. But I really don't think it is a head gasket after The compression test i did. And I know the iac sensor can cause a changing idle like that but I dont think that is the case here since b4 I swapped spark plugs it was running perfectly fine. And as soon as the plugs were swapped it goes into limo mode and the motor wont idle it will almost did then jump up over 1000 and then slowly come back down to almost dying and then pick back up again. it is undriveable... And all I did was change the plugs...

Firestorm500

I HATE Champion plugs.

You could have broken some plug wires internally by handling them.

Severe overheat on your model with the 0331 head probably means cracked head at the least.

Better to get a professional diagnosis before any more money is spent.

Have it towed on a flatbed to a real mechanic or dealership.

Start looking at the autos for sale classifieds.

Turbo X_J

I thought in your original post you were complaining of a "rough idle" after an overheat?

Firestorm500

He's probably got a blown engine.

npk

i have overheated engines before, usually they would run smooth after cooling down completely. i'm not saying that you didn't incur engine damage, but i would rule out the small stuff first. if your problems resurfaced immediately after changing the plugs i would put the old ones back in to see how it runs. there is the possibility that the new plugs weren't gapped correctly. if you have already trashed the old ones check the gap on the new ones. check them all. if one or more of them have been dropped the gap could be closed.

XJ-nick

if it went to crap after you changed spark plugs, then you put the plug wires back on the wrong plugs, meaning that your firing order is off. check the diagram for your model and redo this. My budd just had this exact problem, he actually put a new head gasket on, because he did indeed blow it, was running a good compression too. it's on a 90 model, and when he threw it all back together, it had a hard time starting, and once it did it ran like garbage.

i told him 3 times that it was his plug wire order and he wouldn't listen, today i redid his plug wires and it fired right up and runs like a champ again.

Turbo X_J

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2001 has no plug wires.

tiwvr1

flashing cel light means servere multiable misfire. Check the boots on the coil pack for arcing, and GAP and check the plugs, check compression again.

XJ-nick

ahhhhhhhhh i retract my statement.....