The 1st problem was an overheating one re:https://www.cherokeeforum.com/f2/run...ent-why-56705/, while it was overheating it ran fine until it got too hot. After that repair it started running crappy, runs OK until it gets to operating temp then all hell breaks loose. Lacks power, and when I get off the gas to break the Jeeps sputters very badly and most of the time dies and takes a bit of work to get started again, but the temp stays down; no overheating anymore, just crappy running and has gotten worse as time gone by. I did the self-diagnostic routine as said in the repair manual; starting the engine, getting it up to 2,500rpm, running the A/C briefly, cycling through the gears, then turning the ignition on and off rapidly 2 times then leaving it in the "on" position. Did that three(3) times and the check engine light and dash flashed the code which read 12 and 55; 55 being the end of reading indicator. #12 says "Battery voltage to PCM disconnected within 50 key-on cycles". What exactally does that mean and was it because I had to unearth or take the negative ground off the battery to change out the electric cooling fan to replace the water pump as stated in the earlier post, it ran fine before I did that? No other codes are coming up just that one. I guess I could have left the neg. on while changing the fan but the repair manual said to unearth it less the fan start on its own somehow causing injury. How do I get the PCM back to default? Take the batt. off again and leave it overnight or something? Any suggestions welcomed.

 

those codes are normal it is just telling you that the power was taken away from the ecm dont worry about itrecheck to make sure you did not leave any wires or hoses off when you did the pump

 

1st thing I checked but since I only had to disconnect the fan and nothing else I could not figure what could have gotten undone but I checked anyhow, plus checked for vacuum leaks and found nothing there. How or why does taking power away from the PCM cause it to run crappy and how to undo it?

 

thats not making it run crappy how hot was hot these heads ar famous for cracking after overheating

 

Not hot enough for that. When it got hot and the tappets started rattling I would pull it over and let it cool. Also did a compression check and all were in range, #4 cyl was at the very low part of the range but it didn't affect things before the W/P replacement. There is also no oil in the water, or visa versa nore is there any water or steam dumping out the back. I am fairly confident it is not a blown or warped head.

 

thats hot enough run it get it warm and pull the plugs look for water on plugs

 

When I did the compresion test there was no water on any plugs, they were dry.

 

Update:
I tried to see how it would idle with the temp sensor and the TPC disconnected, still idled like #*@*. Reconnected the leads and did the "key trick" again, now it says code number 12, 45, 22, and 55. I don't have turbo so where 45 came from I don't know. Is it going to run crappy no matter what I do until I erase the codes from the PCM? And how does one do that anyhow?

 

How long did you drive it after it overheated? You said you would pull over and let it cool. Have you tried a compression test after the motor is warmed up and running like sh#t? You will have to pull your head to get it checked, you can't just look at it and say it isn't warped. I had a S10 with a blown head gasket, it was between the water jacket and the number one cylinder, no water in the oil, no steam, I eliminated everything else, then pulled the head. Sometimes you have to take parts off to check them out. If you are not certain then take it to the dealer or a indy shop and let them tell you what it is.
This is my third Jeep, I love them. I have a 2000 that I just bought with 178,000 on it with a knock in the motor. I got it cheap and bought a new long block for it. Should be finished this weekend. All I am saying is a Jeep is like anything else, they break. You need to take yours to a shop, then let us know what the problem is.