low idle at start up

Just bought a 93 XJ that is wrecked for the motor for one of my other XJ's. It runs good but when you first start it it idles low and does not want to run well until it gets warmed up. After it comes up to temp it runs fine. I have checked nuthing so far. Where should I start?

If it runs fine when warm, and the compression is good, then don't worry about it until you have transplanted it. It may just be a sensor problem, and if you use the sensors in the recipient XJ the problem may no longer exist.