When do egr valve work

Increased fuel consumption is caused when the valve is constantly open. This is because the temperature is lower so fuel does not burn at the optimal temperature and as a result is less efficient.

Stalling when the engine idles like a rough idle is usually caused when the EGR valve is permanently open and is constantly letting exhaust gases into the EGR system. You can usually smell fuel if there is a continuous flow of exhaust gases into the intake manifold, because at low revs not all the fuel burns.

This means the amount of hydrocarbon gases emitted from the tailpipe increases significantly producing a fuel smell. Your engine management light may stay on once your car detects an issue with the EGR valve. This could be caused when the EGR is either constantly closed or open.

However, it is worth noting that usually the EGR valve starts to degrade before it fails completely and the engine management system may not pick up on it until it actually fails. Therefore it is worthwhile looking out for the other signs and symptoms mentioned.

As aforementioned if the valve is stuck open the temperature is lowered which prevents all the fuel from burning. This means an increased flow of unburned hydrocarbon gases coming out of the tailpipe.

While if your valve is always closed the high temperatures in the combustion chamber allows excessive formation of NOx gases. Knocking noises from the engine can be caused if the EGR is constantly closed. This is because at low rpm the fuel ignites early when it meets the high temperature. Detonations are also common as a second ignition can occur after the normal ignition. Some of the same engine performance problems which are indicative of an EGR valve failure can also indicate problems in other parts of the system.

This can include the likes of faulty spark plugs, spark plug wires, fuel filters, fuel pump regulator or engine sensors.

Increased hydrocarbon emissions can be a result of a leaking fuel injector, bad injection timing, bad cylinder compression or a bad oxygen sensor.

Many EGR valves now incorporate a cooler to decrease the temperature of the exhaust gas. Early designs used vacuum to operate the valve mechanism whereas most modern types are electronically operated by solenoids or motors.

Exhaust gas flows through the valve and most of the time it is diverted through the cooler where the gas is cooled by the engine coolant. The cooler bypass operated by a vacuum diaphragm is only in the closed position when the engine is cold. This helps to get the engine up to the optimum operating temperature quickly. The motor cam moves the re-circulation valve in or out to control how much exhaust gas is allowed back into the inlet.

The logic by which the onboard diagnostics detects trouble follows one of two routes. On some applications, a code 32 is set when the computer detects a richer fuel mixture off idle indicating no EGR. On others, a code is set if the computer energizes the EGR vacuum solenoid but does not detect a corresponding drop in intake vacuum.

It works like a throttle position sensor, going from high resistance ohms when the EGR valve is closed to low resistance ohms when it is open.

Other codes include a code 32 which indicates the EGR circuit is not controlling. Both indicate an electrical problem in one of the solenoid circuits. The solenoids should have between 30 and 70 ohms resistance. See Emission Guide for emissions testing and diagnosis information.

Emission Guide is a quick reference program that covers basic emission controls and emissions testing. It provides a feedback signal to the engine computer so it can vary EGR flow to meet changing engine loads. The DPFE sensor is usually mounted on the engine and is connected to the pipe that runs from the exhaust manifold to the EGR valve with two rubber hoses.

Does the engine have a detonation spark knock problem when accelerating under load? Refer to the timing specs for the engine and check ignition timing. The timing may be overadvanced. If the timing is within specs, check the engine's operating temperature. A cooling problem may be causing the engine to detonate. Be sure you've ruled out all the other possibilities before focusing on the EGR system.

Use a vacuum gauge to check the EGR valve vacuum supply hose for vacuum at rpm. There should be vacuum if the engine is at normal operating temperature.

No vacuum would indicate a problem such as a loose or misrouted hose, a blocked or inoperative ported vacuum switch or solenoid, or a faulty vacuum amplifier or vacuum pump in the case of a diesel engine.

Refer to a vacuum hose routing diagram in a service manual or the hose routing information on the vehicle's emission decal for the location of the solenoid. If the solenoid fails to open when energized, jams shut or open, or fails to function because of a corroded electrical connection, loose wire, bad ground, or other electrical problem, it will obviously affect the operation of the EGR valve. If bypassing the suspicious solenoid with a section of vacuum tubing causes the EGR valve to operate, find out why the solenoid isn't responding before you replace it.

The problem may be nothing more than a loose or corroded wiring connector. Inspect the EGR valve itself. Because of the valve's location, it may be difficult to see whether or not the valve stem moves when the engine is revved to to rpm by slowing opening and closing the throttle.

The EGR valve stem should move if the valve is functioning correctly. A hand mirror may make it easier to watch the valve stem. Be careful not to touch the valve because it will be hot! If the valve stem doesn't move when the engine is revved and the valve is receiving vacuum , there's probably something wrong with the EGR valve.

Vacuum should pull the valve open creating the equivalent of a large vacuum leak. This should cause a momentary drop in idle speed and a noticeable increase in idle roughness. Air from the environment, mostly a combination of Oxygen and Nitrogen, combines with fuel and ignites inside the combustion chamber, temperatures increase and produce NOx emissions.

The EGR system works by returning a small portion of exhaust gas to the engine's combustion chambers through the intake manifold, lowering combustion temperatures and therefore reducing the amount of NOx emitted. It connects the exhaust manifold to the intake manifold and is controlled by either a vacuum or a built-in electric step motor. The function of the EGR valve is to control the flow of exhaust gas being recirculated depending on the engine load.

Nitrogen oxides are emissions produced as a by-product from the process of combustion, Nitrogen and Oxygen gases in the air react during combustion, especially at high temperatures. NOx is a major component of smog and can have detrimental affects on human health as well as well as ecosystems and agricultural crops. Therefore, incorporating EGR systems into the design of a car is important with regards to lowering harmful emissions to save the environment and have a positive impact on human health.

The majority of modern vehicles incorporate EGR valves into their design to reduce NOx emissions and therefore meet stringent emissions regulations.