Quote:
Originally Posted by bwostosh
Should be same idle speed cold or hot,
that is the purpose of the air valve (the can type thingy at the front of the intake manifold) which gets its input from the coolant passage, The thermostat can affect this.
This system relys on everything being correct.
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This isnt a modern idle control valve managed by the ECU its a wax filled piston that expands as the water temperature increase and slowly reduces the air bypassing the main throttle. The idle screw sits alongside and allows additional air to pass. It's basic and doesnt provide a perfect idle under all conditions.
From memory I think the overrun circuit kicks in at 1,500 rpm but as already said 800 should be about right when cold and the outside temperature is low, any higher and your giving the trans a big thump when you engage drive.
I'm guessing your local weather has improved recently and this has caused the cold idle to be higher than during the winter.