Engine performance issues: if the valve is stuck open the vehicle’s air-fuel ratio will be disrupted causing engine performance issues such as reduced power, poor acceleration and rough idle.Check engine light: as with most engine management components, a problem with the EGR valve may trigger the check engine light.However, there are a few signs to look out for: The symptoms associated with EGR valve failure are similar to those of many other engine management components, and because of this EGR faults continue to be a source of headaches for many technicians. What to look out for in a failing EGR valve? Failures can also be caused by a rupture or leak in the valve diaphragm. Over time this will clog tubes, exhaust gas channels and eventually the valve’s plunger mechanism, causing it to either stick open or close. However, the single biggest cause of failure is the buildup of carbon particles from the exhaust gases along the EGR and intake system passages. Why do EGR valves fail?ĮGR valves operate in a hostile environment so over time will experience wear and tear. These valves receive a pulse width modulated signal from the ECU, to regulate exhaust gas flow.
Some valves also include a feedback sensor to inform the ECU of the valves position.ĭigital EGR valves feature a solenoid or stepper motor and, in most cases, a feedback sensor. Vacuum operated EGR valves use a vacuum solenoid to vary the vacuum to the diaphragm and, in turn, open and close the EGR. The vacuum created by cylinder depression, draws the exhaust gases in and the flow is regulated by the opening and closing of the EGR valve itself. Gasoline EGR valves divert the exhaust gases, much like the high pressure diesel equivalent. The gas is then passed back to the inlet manifold via a pipe. A secondary valve is also used to help create a vacuum in the inlet manifold as this is not naturally present on diesel engines.ĭiesel Low pressure EGR valves divert the exhaust gas after it has passed through the diesel particulate filter - this gas has a lower flow but is almost completely clean of soot. The gas is then passed back to the inlet manifold either via a pipe or internal drillings in the cylinder head. Types of EGR valveĪlthough there are several types of EGR valve - earlier systems use a vacuum-operated valve, while newer vehicles are electronically controlled - the main types can be broadly summarized as:ĭiesel high pressure EGR valves divert the high-flow, high-soot exhaust gas before it enters the diesel particulate filter – the soot can combine with the oil vapor to create sludge. In diesel, it can also help to reduce diesel knock at idle.
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However as more torque and power is required, for example during full acceleration, the EGR valve closes to ensure as much oxygen enters the cylinder.Īs well are reducing NOx, EGR valves can be used in downsized GDi engines to reduce pumping losses and improve both combustion efficiency and knock tolerance. During idle and at low speeds, only a small amount of power is required, and therefore only a small amount of oxygen, so the valve gradually opens – it can be up to 90% open at idle. The EGR valve is closed when the engine is starting up. The EGR valve has two primary settings: open and closed, although the position can vary anywhere in between. With less oxygen, the now diluted mixture burns slower, lowering temperatures in the combustion chamber by almost 150☌, and reducing NOx production for a cleaner, more efficient exhaust. To help minimize this, the EGR valve allows a precise quantity of exhaust gas to re-enter the intake the system, effectively changing the chemical makeup of the air entering the engine.
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However, when it is exposed to the extremely high temperatures in the combustion chamber, plus 1370☌, the normally inert gas becomes reactive, creating harmful oxides of nitrogen or NOx, which are then passed through the exhaust system into the atmosphere. Nearly 80 percent of the air we breathe is nitrogen. Examples of harsh environments for EGR valves.
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