MTI, 09 wrote:
What is the thinking behind a coasting richer solenoid system? I notice if Im going downhill on the highway instead of using the brake a lot if I just barely touch the gas pedal the truck seems to slow more than if I simply coast in gear.
It's an emission thing. On a carb vehicle when coasting with the throttle closed the air is shut off but some fuel is still drawn in through the idle circuit giving an improper burn, ( read high emissions). That is the put-put-putting sound you sometimes here out the exhaust while coasting down from speed.
The coasting richer thing opens an additional path with the proper mixture for a cleaner burn. Yes, it causes the truck to not slow as quickly as it could. It's just the way the Japanese decided to tackle the problem on our trucks.
Mafoose is correct, check the anti-dieseling solenoid if you are having idling problems.