Engine idle control

A reciprocating internal combustion engine having a combustion chamber defined by a cylinder bore and a piston reciprocating therein, an induction system for delivering at least an air charge to said combustion chamber, said induction system having an induction passage terminating in an outlet opening the flow through which is not directly controlled said piston and a butterfly-type throttle valve supported for rotation about a throttle valve axis in said induction passage for controlling the flow therethrough, said throttle valve having a peripheral configuration which is substantially complementary to the shape of said induction passage when said throttle valve is in a closed position at an angle in the range of about two degrees to twelve degrees (2.degree. to 12.degree.) to a plane containing said throttle valve axis and extending generally perpendicularly to the flow through said induction passage for preventing flow between the periphery of said throttle valve and said induction passage when said throttle valve is in such closed position, and means for providing a bypass air flow directly through said induction passage and past said throttle valve for at least engine idle air flow when said throttle valve is in said closed position.