alright everybody. I've tinkered with cars my whole life and was ready for a challenge. My 98 XJ engine blew so I went to a wrecking yard and bought a wrecked 4.0. Took it apart and off to the machine shop. So, here I am with a motor I built, I got it in and guess what??? It starts and sounds great! Only problem is that it won't idle. As soon as I let of the gas it just dies. If I rev it up it sputters. So, did I mess up the timing or do I have some other issue? Help, the new builder may have not really been ready.

 

Well, I should say it sounds great at 2K rpm. Rev it up and it sputters and cuts out, let off the gas and it just dies.

 

Map sensor from the sounds of it

 

Vacuum leak, IAC & TPS hooked up/functioning?

 

After doing a headgasket job on my XJ for a long time i had this same problem , mine turned out the battery was bad just throwing it out there! lol