Two-Port EGR System (900)

Exhaust gases (from exhaust port of number 2 cylinder) are routed through the cylinder head, and then through a steel pipe, to EGR valve in inlet manifold. See Fig 1 .

Fig 1: Cutaway View of Two-Port EGR System (Non-Turbo Models)

Opening of the EGR valve, when coolant temperature is below 112°F (43°C), is regulated by 2 adjacent vacuum ports in throttle valve housing. At idle, vacuum is not applied to either port, resulting in a closed system. See Fig 2 .

Fig 2: Two-Port EGR System Operation (Non-Turbo Models)

At off-idle or low speed cruise, vacuum is applied to port number 1 only, resulting in a partial signal to (and a partial opening of) the EGR valve. When throttle valve opens past the second port, a full vacuum signal is applied to the EGR valve.