Previous owner chased a high idle & rich burning condition for a couple of years. Said he could never cure it. TPS, MAP, EGR, EGR solenoid, Vacuum lines - after clearing all the codes and hitting all the common sense items (tune-up, hunting for vacuum leaks, etc) he gave up and just lived with it. I erroneously figured that a bad ECT sensor....would show in a bad read on the temp gage. NOT SO - The temp sending unit down low on driver's side talks to the temp gage inside. The ECT sensor mounted next to the water outlet up top is the one that talks to the computer. For 2 years he dealt with high idle rich running. a $10 sensor and it sows down right nicely when warm. Makes sense when you realize that the computer was fueling a cold engine all the time until the defective sensor was replaced.