Auxiliary Air Valve
Truck not idling. Lousy gas milage.
? Should the hose conecting the Aux.air valve to
the throttle valve have a negative vacume. Pull it
off and it sucks air.
Check for vacuum leaks. Spray some brake cleaner around the throttle body and the vacuum lines. See if there's any noticeable difference in idle. If so, you have found the leak. You may also have a bad Idle Air Control as well. You may want to replace that. I would also buy some throttle body cleaner and thoroughly tear down and spray the entire throttle body. Excess carbon behind the throttle plate will cause a lot of problems. If the Aux Air Valve is connected to the throttle valve, then I would suspect that it should have a negative vacuum. The throttle is constantly sucking in air and fuel, so it would make sense.
Here's a pic of the Idle Air Control valve.
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