I have a 1997 Checvy 4.3L with 131k miles. During normal dry days, truck runs perfect. On humid, rainy (or foggy) days, truck starts fine by misfires badly at 2000 RPM. Shifting to next gear and lowering the RPM, misfire/stumble is gone. This repeats in ALL gears. Will not however, Check engine light is on with a Bankone Oxygen Sensor failure. But dealer said will not cause the problems I'm having.
Have replaced Intake Air Temp Sensor, MAF Sensor, TPS, New plugs, new wires. HELP!