Disconnect vacuum hose from EGR valve "A" and connect a vacuum gauge to it. On Man. Trans. models, disconnect and plug vacuum hose from VCV.
On all models, start engine and run at idle speed. With coolant temperature below 113°F (45°C), vacuum gauge should indicate zero at 2500 RPM.
As engine warms up, vacuum gauge should indicate high vacuum. If not, check BVSV and modulator.
On Man. Trans. models, reconnect and pinch off hose to VCV. Make sure vacuum gauge still indicates high vacuum at 2500 RPM. Release hose. Vacuum gauge should indicate zero.
On all models, disconnect vacuum gauge and stop engine. Disconnect and plug EGR vacuum modulator exhaust gas hose. Start engine and race it once.
With engine idling, apply vacuum directly to EGR valve. Engine should run rough or die. Reconnect vacuum hoses.
If system performed as described, it is operating correctly. If not, test individual components and repair or replace as necessary.

Fig 1: Supra EGR System

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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.

Safety Warning

EGR System: Supra