Device
An exhaust gas recirculation system is used to reduce peak flame temperatures in the combustion chambers. A small amount of exhaust gas is expelled from the exhaust manifold and reintroduced to the intake manifold, where it mixes with the supplied air/fuel mixture and enters the cylinder. At a lower combustion temperature, the content of nitrogen oxides in the exhaust gases decreases.
The RVG system consists of an RVG valve that regulates the flow of exhaust gases, as well as various vacuum and electrical control devices that prevent untimely operation of the RVG system. There is no need for an EGR when the engine is cold enough to lower the temperature of the flame in the engine. The use of RVG in this case would lead to unstable engine operation, so the RVG function is disabled by either a thermal valve or a fuel injection computer (coolant temperature control). In addition, the RVG is also turned off when idling on a warm engine in order to prevent the occurrence of unstable revolutions or «jerking» when pressing the accelerator pedal (gas).
Lowering the combustion temperature also leads to some reduction in power. Therefore, when the engine enters the wide open throttle driving mode, the EGR function is disabled. Typically, the vacuum applied to the RVG valve overcomes the tension of the spring inside the valve and keeps it open. At wide open throttle, the vacuum acting on the EGR decreases and the spring closes the valve. A common symptom of a RVG malfunction is slight engine knock at part-open throttle, most noticeable under load, i.e. when climbing a mountain or when carrying several passengers. The RVG valve can cause erratic and uneven idle speeds. If the engine is adjusted correctly, and other reasons (vacuum failure, poor quality spark plug wires) eliminated, then when unstable idle speeds appear, the malfunction lies in the RVG.
Examination
With the engine cold, disconnect the throttle body vacuum hose.
Plug the pipe from which the hose was removed. Start the engine. On fuel injected engines, the EGR system will not maintain vacuum when the engine is cold and idling.
Warm up the engine to normal operating temperature. Before checking, the temperature of the coolant should be 80-85°C. Using the pump, create a vacuum of 30-43 mm Hg. Art. The RVG system must maintain a vacuum, while idling will not be accompanied by noticeable changes.
On a fuel injected engine, let the warm engine idle as above. Create a vacuum of 83 mm Hg. Art. and listen to the operation of the engine. When the desired degree of vacuum is reached, the idling will become unstable, uneven, the engine may even stall as soon as the RVG valve opens and passes the exhaust gas. The system must maintain a vacuum with the valve ajar.