I just did a motor swap and the motor I used was just a long block an I swapped all the sensors and accessories from the old motor to the new I have it running but it has a rough idle and stalls out after a few minutes and the mil lights on for ckp code any thoughts ? 98 xj classic 173,000 body 81,000 motor

 

This may be irrelevant but a member on another forum stated the following, concerning the bonding strap that goes from the firewall to the left rear cylinder head bolt:

"I had to replace that very ground 2 weeks ago. I touched it and it literally crumbled. Stalled 6-7 times on the way to work and the check engine light came on. I chuggled it 2 miles to autozone. They scanned it and it was throwing a P1391code. I replaced the wire on the spot. The 99xj started and ran fine. Engine light went out on my way home. Oh how relieved I was!!!"

 

Didn't work but thanks for the advice

 

What code(s) do you get?

 

P1391

 

P1391 could be a cam sensor as well. Code should be for an intermittent signal from the crank or cam sensor.

 

Definition

 

Yup, I've seen that code be related to both cam or crank sensor.

But the crank sensor fails more frequently than the cam sensor does on the 4.0

If you end up buying a crank sensor, buy a Mopar unit from Jeep. Aftermarket crank sensors are "hit and miss" with a lot of miss....