Throttle valve check
Checking the condition of the throttle valve is very rare. Sometimes the cause of engine idling problems can be the throttle valve itself.
In gasoline engines, the throttle regulates the engine speed. It is located on the intake pipe and controls the airflow as a valve. In idle mode, the throttle is closed and lets in the minimum amount of air sufficient to keep the engine running at the lowest set rpm. However, when the engine is cold and in the warm-up phase, a slightly higher mixture is needed, which requires more air to be passed through the bypass line or by moving the throttle valve. When the engine is warmed up, the mixture is adjusted at idle to maintain the set rpm.
When there is an oil leak and its combustion, the purity of the exhaust gas and intake manifold is disturbed. The soot in the exhaust gas is introduced into the intake manifold via the EGR valve. Also, engine oil can enter the intake manifold through damaged intake valve guides or the turbocharger (if equipped). Over time, these impurities accumulate on the walls of the intake manifold in the throttle body, preventing the passage of air when the throttle valve is closed. An engine with less air flow at idle has an unstable operation, chokes and dies.
Checking the throttle valve can be done by removing the intake hoses or the throttle module. Inspection of the inside of the throttle valve body determines the condition. If deposits are visible on the walls of the intake manifold in the part of the throttle valve, it is necessary to clean it. While the throttle valve is in the zero position, the module is redirected towards a bright light. By observation, we can see the light around the entire circumference of the valve towards the walls. The space between the valve and the module wall should have a paper thickness, which is enough to allow air to pass through in idle mode. Dirty walls prevent the passage of light and this is a sign that the module is dirty.
Before cleaning the throttle body, remove all non-metallic parts such as sensors, regulators and gaskets. Cleaning is done by applying a grease remover and wiping with soft cloths. Remove the dirt without scraping so as not to damage the surface of the walls of the suction line. Compressed air blows out all passages on the throttle body and dries the inside.
To check the throttle valve, follow these steps: