My dad,s '78 280 won't pass idle test for smog. Co's too high. Lean's out just fine at higher rpm. Replaced injector's, tried different air flow meter's, computer's, checked harness and reading's are fine. Any idea's?

Have you checked the position of the throttle valve switch to make sure that the idle contacts are closed at idle?

Edited March 11, 200917 yr by sblake01

Found out valves were way out of adjustment. Thanks