all right guys dropped a rebuilt junk yard motor in my jeep about a year ago from a 1998 grand cherokee. when i put it in it took a couple days for the computer to catch back up. well just recently i wasnt paying attention driving down the highway when i believe the thermostat got stuck shut and i overheated and crack the head. i had an extra 95 head of a cherokee and had my machine shop (gregorys machine shop in virginia beach) to rebuild it and check it out. it checked out and they put all new parts in and on the head. i put it all back together with good gaskets and torqued everything to spec and made sure i put 95 plugs in the head to insure the right gap. well it started right up and sound good it just has a low idle at first then when you start driving it works great but it feels a little weird. all my gauges are in great shape oil pressure, water temp etc. the jeep sat for a month and half before i fixed it.

So i guess what my question is, do you think its the computer again that has to catch back up or does it need a tuning or what?

let me know what you think thanks

 

Anybody?

 

i think if you heated it up enough to crack the head then the block and pistons did not go untouched. do a compression test and make sure you have the right plugs in there for a 98. you can use them from a 95 for the head but they need to be gaped the same as a 98 (if the gap is even different). but i would do a compression test first and then check your vacuum hoses

 

The block in all is good it was a weird crack cuz the head gasket was fine and all just the head had a tiny crack and the no coolant mixed with the oil either. The oil was clean ill run a compression test tomorrow and see what's up but i punched on the highway and it has a lot of power so idk

 

Oh and i have 95 plugs in it cuz its a 95 head

 

Is the gap for the plugs and plug type the same for 95 and 98?

 

yea i got that part, just make sure that they are the same gap as a 98 head cause your computer is trying to burn fuel with the stock gap of a 98 not a 95. so just check them. also the 98-99 heads are prone to crack, i believe there was a recall or warning put out about them.

 

They are but its in a 91 cherokee maybe that's it ill check

 

Just checked they are all .035

 

No the head warning was for late 99 thru 2001 not 98. But remember any 4.0 head is prone to cracking with any overheating.Also unhook your battery with the headlights on for 3-4 minutes then shut headlight switch off and hook battery up and let your computer relearn maybe that will help.

 

Hook it back up while running?

 

no i think he means turn the car off, turn the head lights on, pull the negative battery cable, wait 4 min and then turn the head light switch off and reconnect the battery. then start the car

 

Ok ill do that tomorrow

 

Yes not running sry but turn lights on first then disconnect negative battery cable ,wait 4 min then turn headlamp switch off re connect battery. By disconnecting battery with light switch on you drain the power left in the computer so it will have to relearn, you can also disconnect battery both positive and negitive and touch cables together for a few minutes, but I like the first way told to me by a dodge,jeep mechanic.

 

Allright ill let you know if that works