Symptom: cold start problems, unstable idling after starting, idling normal hot car.
Troubleshooting: This phenomenon preliminary judgment is affected idle speed stepper motor failure, the need for dismantling. Turn the ignition switch, remove the stepper heavy duty diagnostic tool motor, found the head cone valve and seat stepper motor idling intake clogged with oil, the impact of idling condition into the air, the oil washed with dry cleaners, installed good stepper motor, start the engine, smooth idling, failure to eliminate.
Failure Analysis: This car idle condition according to the computer by the engine battery voltage, coolant temperature, engine load and engine speed to calculate the optimum idle speed stepper motor position and instructs the cone valve with a small amplitude, or the stepper motor forward or back change idle inlet section to control the engine idle smooth operation.
During cold start, the coolant temperature is low, the engine computer instruction fuel injection pulse width is increased, while the idle speed stepper motor command conical valve opening increases, the high idle speed of the engine operation, the temperature was gradually car key replacement increased as the cooling liquid, spray oil width decreases, idle speed stepper motor conical valve opening is reduced accordingly, to keep the engine at low idle.
Such failure is due to the oil cone valve and valve seat accumulation, reducing the adjustable range cone valve, resulting in cold start, the intake air is reduced accordingly, and the emergence cold start problems and not idling stable.
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