I own an 1995 Dodge Caravan with a 3.0 motor with 82,000 miles. The problem is that this vehicle recently failed the PA state emissions test. The problem is that the hydrocarbon level is high at idle but drops down to an acceptable level at 2500 RPM. I have since replaced spark plugs, spark plug wires, distributor cap, rotor, PCV valve and a bad fuel injector only to have the same results on retest. It runs a little rough at idle but runs fine off idle with no hesitation. My next step would be the oxygen sensor. Any suggestions greatly appreciated.