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 is accomplished by lowering peak combustion chamber temperatures. To do this, recirculated and metered amounts of exhaust gases are reintroduced into engine through intake manifold, where they are mixed with the incoming air/fuel mixture.
Two types of EGR systems are used, depending upon vehicle application. These are vacuum modulated and backpressure. Some engines may also use what is called "pulse width modulation". The ECM turns an EGR vacuum control solenoid on and off many times per second, varying amount of "on" time to vary amount of EGR. For more information on ECM controlled EGR systems, see the appropriate article in the COMPUTERIZED ENGINE CONTROLS 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.
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