I have been working on a jeep i picked up cheep a few months ago and its still having problems, some times it runs nice and some times it runs like it has a bad miss. The guy i got it from had just redone the top end and gave up on it.
It warms up really fast, cold to 210 in half a mile in 40 degree weather and the radiator hoses are rock hard. Im sure if the two problems are related but im thing it could be a bad head gasket. Everything in the cooling system is new so are the injectors and the throttle body. The oil is clean but Im thinking a bad head gasket could be causing the high pressure and burning coolant could be causing the miss. What do you guys think, any other ideas?

 

I'd agree on a leak from combustion to cooling system, head, head gasket, etc.
What year is it?

 

hoses are rock hard? That could be a sticking thermostat too. I had a truck years ago that had a stuck t-stat and it would do the same thing in winter. Got super hot super fast. Also, are you running a good antifreeze mix?

 

Its a 91, im going to do the test on the coolant tonight. The thermostat is working fine and it has 50/50 antifreeze.

 

A sticking t-stat will not cause excessive cooling system pressure ......a bad rad cap will.

 

We have a winner, bad radiator cap, the coolant test was good so i took the cap off my other 91 and it fixed it.
Now I still have the problem of the intermittent running rough. I have tried just about everything i can think of plugs, wires, computer, throttle body, injectors. I have 2 91's and a spare motor so parts are easy to swap out and test but im running out of ideas.

 

Today I did a lot of testing and found the #5 cylinder is not firing. It has good spark and fuel. I tried different plugs and swapped injectors but the problem stayed in cylinder 5. I will do a compression test tomorrow.