Electronic engine control for regulating engine coolant temperature at cold ambient air temperatures by control of engine idle speed

Abstract

An electronic engine control for reducing, and ideally eliminating, accumulation of products of incomplete combustion that result from cold ambient conditions acting on the engine and that otherwise might ultimately affect engine operation before the useful life of an engine has elapsed. An idle speed control has a first source providing a signal corresponding to ambient air temperature, a second source providing a signal corresponding to engine coolant temperature, a third source providing a signal indicating that an engine is running substantially in an idle condition, and a processor that processes the signals from the first source, the second source, and the third source to develop an idle speed control signal for controlling engine idle speed by regulating the engine coolant temperature to a defined coolant temperature when the engine is running in an idle condition and the ambient air temperature does not concurrently exceed a defined air temperature. The engine coolant temperature is regulated to substantially 63° C. (145.4° F.) when the ambient air temperature does not concurrently exceed substantially 0° C. (32° F.). Also included are a proportional and integral control that processes an error signal developed from engine coolant temperature feedback to the processor to develop the idle speed control signal, and a fault detection circuit.