Hi Guys, I've exhausted my own knowledge trying to figure out what might be the issue here, short of replacing a bunch of stuff and spending a lot of money I don't have.

I have a 1990 Cherokee 6cyl 4.0 4wd with about 170k miles on it. I loaned it to my buddy the other day and he sat in stand still traffic for an hour and overheated it. He said he saw a small amount of steam (there's a small leak from the hose on the bottom o the overflow reservoir) so he pulled over. The temp gauge wasn't all the way to the red. He went to restart it and it turned over but would not start. I tried to start it for the next two days and on the third day it finally started up.

I burped the coolant system, and spilt a fair bit of coolant when I did because the motor was still warm.

I also removed the IAT sensor and cleaned up as it was very very black and covered in nasty. However i dropped it and the little cage around the sensor snapped off, although the sensor still looked okay, So i reinstalled.

Went for a drive and it ran rough and stalled on me after about two minutes. Turned the key and it started right back up. Same thing, dies two minutes later. Repeat 10 times on the way back to my buddies house. Starts right back up and runs for a couple of minutes before stalling again. Smells terrible and has a bit of white smoke coming from tailpipe, which leads me to think possible head gasket failure?

I'm trying to track down a replacement IAT sensor, which has been difficult. I'm also swapping plugs tonight and checking for coolant in the cylinders. Probably going to try to put some Barq's in the radiator to see if it helps plug up the head gasket as a very short term replacement. I have that work before.

Went for a drive when it was cool out last night and she ran rough but did not die.

Any suggestions as to where to place my focus are very welcome. I just think it's so strange that it starts back up. I'd almost think fuel delivery, but the likely hood of a fuel pump going out at the exact same time as an overheat seems too sad to be true.

Thanks again for any help you provide! I wan't to get my baby back in good shape!

 

No need to throw parts at it, a compression test and a cooling system pressure test can be done with free tool rentals from autozone. Fuel pressure too, but I think your symptoms are mostly coolant issues.

I would'nt keep trying to run it till you do some testing, water and engine bearings don't play well together.

 

Good Idea. I'm sure there's a thread on here that will walk me through what the numbers should be.

Thanks for the suggestion!

 

I would definitely look t the plugs too. I have had plugs get fairly fouled if the engine wasn't running quite right. Once they get fouled, starting can be difficult. When I have had that happen a new set of plugs really helps. Lot's of cranking without a start will definitely make the plugs pretty nasty.

 

That wa any first thought. Three days of turning it over a bunch definitely cannot be good for the plugs!

 

Found the culprit. The vacuum line from the MAP sensor came unplugged! It was as easy as that. I checked all the other vacuum lines but forgot about that one. Seems to be running fine now.