My Dodge D150 idle is set to 750 RPM (Auto transmission) in neutral and it warms up and idles at 750 RPM in neutral. Once I start driving the truck when I stop, the idle increases to 1100 in neutral (825 RPM in Drive.) I can shift to neutral and blip the throttle to 3000 RPM and it resets to 750 RPM. It usually takes three tries to get it down to 750 RPM. I have the factory Holley 1945 carb with the factory dual return springs and the small spring on the downshift rod. I have lubricated everything that moves on the carb and transmission linkage and it still does this. I have the Idle Stop Solenoid installed on the carb but it does not advance the throttle when the A/C comes on. I don't think it is getting any power to the solenoid. The carburetor linkage does not stick at all when operated by hand. Should I replace the accelerator cable or is there some internal problem with the carburetor? It is a new rebuilt unit from Rock Auto and otherwise works perfectly. The EGR valve is connected and works when tested staticly but I don't know if it works when the car is running.

Something is hanging up between your foot and carburetor. Next time the idle refuses to drop to 750 rpm, without touching the gas peddle, turn off the engine, open hood, remover air cleaner, and operate throttle by hand while observing all the linkage. At some point, whatever is hanging up will let go, and you will see it move. This may take several attempts, as these parts are tricky to catch in the act sometimes.

Don’t discount a worn accelerator cable that may be frayed on the cabin side of the fire wall as well. Also inspect the kick-down or throttle pressure cable / linkage.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Thanks! It was the fast idle cam holding the throttle open on the lowest level. I adjusted the fast idle screw out and bent the choke rod to position the screw below the fast idle cam and to fully open the choke.

Well there, that was easy!

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC