I recently purchased a MotorCraft 2100 rebuild this gentleman on eBay for my 89 YJ 4.2 6cyl. Good reputation 100% feedback and tons of satisfied customers on the replies. When I initially put in the carb it ran real rough. It doesn't idle well and it would shut off almost instantly after a long drive (30-40 mins). It sputters and almost dies when you give it 1/4 throttle but when you floor it runs. I followed a diagram for the vacuum install and it all seems ok.
Took it to a carb shop today to tune it and they told me the choke was bad and the brake booster was bad causing vacuum issues. They plugged up the brake vacuum port and they say it runs 100% better. I'm going to pick up Jade tomorrow.
Any suggestions as what to do to get my YJ running right?