EGR Function Testing - Toyota: Other Toyota Prius Plug-in

1974-93 All Models Except Diesel

1. Disconnect vacuum hose to EGR valve. Using a hand-held vacuum pump, apply vacuum to EGR valve with engine at idle. Engine should run rough or stall. If engine does not run rough or stall, check EGR valve passages for blockage or faulty EGR valve. Clean passages as necessary. If passages are clear, replace EGR valve.
2. Install vacuum gauge to ported vacuum port to EGR. Raise engine RPM. Vacuum should be present. If vacuum is not present, clear vacuum port of blockage.

Note. For systems equipped with a double or single diaphragm type EGR valve, perform the following tests

Double Diaphragm Valve

Ensure all vacuum hoses are routed properly. Warm engine to normal operating temperature. With engine at idle, switch hoses on EGR valve, carburetor should make bubbling noise. If bubbling noise is not heard, check other EGR system controls. See appropriate manual for troubleshooting.

Single Diaphragm Valve

1. Check all vacuum hoses for correct routing. Warm engine to operating temperature. Disconnect vacuum hose from EGR valve.
2. With engine at idle, apply intake manifold vacuum to EGR valve. On systems equipped with a modulator and/or auxiliary control valve, engine should run rough or carburetor should make bubbling noise.
3. On systems not equipped with a modulator and/or auxiliary control valve, increase engine speed to 3000-3500 RPM. Carburetor should make bubbling noise. If bubbling noise is not heard, check other EGR system controls. See appropriate manual for troubleshooting.