Chrysler Repair: no trouble codes, obd2 scanner, dodge caravan

Question
I own a 2002 dodge caravan 2.4L A604 41te. Sometimes not all the time engine does not idle smoothly.Thought it might be idle solenoid. Put obd2 scanner on it did not show any faults. Unhooked solenoid engine started running rough, tried scanner again, still no faults. Wife owns 2001 dodge 2.4 3spd auto put scanner on it and it retreived faults.Please whats wrong?

Answer
Intermittents are the hardest to nail down. Since there are no fault codes, I would start with the most obvious. Run some throttle body cleaner through its throat and put some fuel injector cleaner in the tank. The throttle body is the best suspect. It gums up with oil and crud from the PCV and causes almost a miss at idle, tripping no codes.