Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
EGR System - Gasoline: Description
Exhaust Gas Recirculation (EGR) is used to reduce oxides of nitrogen (NOx) emissions. This process is accomplished by lowering combustion temperatures of burning gases. Recirculated and metered amounts of exhaust gases are reintroduced into engine through intake manifold, where they are mixed with air/fuel mixture.
Vacuum modulated system regulates exhaust gas recirculation according to manifold vacuum. Backpressure modulated system regulates timed vacuum according to exhaust backpressure level. Special control valve within the EGR valve housing responds as a pressure regulator.
Some engines use what is called "Pulse Width Modulation". The ECM turns the solenoid on and off many times per second and varies the amount of "on" time to vary the amount of EGR. For more information, see appropriate article in the COMPUTERIZED ENGINE CONTROL section.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.