All Models Except 1989-93 Lemans (Ported EGR Valve)
- Ensure engine is at normal operating temperature. Disconnect vacuum hose at EGR valve. Connect a vacuum pump to EGR valve. Start engine.
- Apply vacuum to EGR valve. If engine runs rough or stalls, and gauge holds vacuum, EGR valve is functioning properly. Connect a vacuum gauge to EGR hose. Increase engine speed to about 3000 RPM. If vacuum is shown on gauge, system is functioning properly.