What is the reason for the unstable idle speed of Toyota Camry 2.0s?

(1) Leakage of intake manifold or various valves.

When air, gasoline vapor and combustion waste gas that should not enter enter the intake manifold, the mixture is too rich or too thin, which makes the engine burn abnormally. When the location of air leakage only affects

When there are individual cylinders, the engine will shake violently, which has a great influence on the idle speed of the cold car. Common causes are: loose clamp of intake manifold or broken hose; Air leakage of intake manifold gasket; The intake manifold is damaged or other parts may suck in air.

Manifold grinding hole; O-ring of fuel injector leaks; Vacuum tube plug falls off and breaks; The positive crankcase ventilation (PCV) valve has a large opening; The valve of activated carbon tank is normally open; Exhaust gas recirculation (EGR) valve is not closed correctly.

(2) There is too much scale on the throttle and air intake.

There is too much carbon and dirt in the throttle and the surrounding air intake, and the cross-sectional area of the air passage changes, which makes the control unit unable to accurately control the idle intake, resulting in the mixture being too rich or too thin, which makes the combustion abnormal. Common reasons are: the throttle has oil pollution or carbon deposition; There are oil stains and carbon deposits at the air inlet around the throttle; Idle stepper motor, duty solenoid valve and rotary solenoid valve are polluted by oil and carbon.