I will try to keep this short. I have a 2002 Focus with 52,000 miles. The motor broke a rod (long story) and i purchased a used motor with less than 20,000 miles on it. The car sat for a year and a half before I was able to repair it. I replaced the motor and started it. The motor starts right up and idles fine when it is cold. When the motor warms up (after about two minutes) it will not idle at all, it just dies. I need to keep the RPM above 1000 or it will just die. If it dies when it is warm it will not start until it cools down. I have noticed traces of oil in the intake manifold. I have checked for vacuum leaks on the intake manifold. I have replace the PCV valve. I have checked everything I can think of. I took it to a local repair shop and they checked the car and could find nothing. They believe it is something internal.
Please help, Any ideas would be appreciated. I have run out of ideas.