Exhaust Gas RECIRCULATION (EGR) System
NOTE:
DO NOT
warm the engine until specified. Some testing must be performed when engine is cold.
- Remove cap and filter from top of EGR vacuum modulator. See Fig 1. EGR vacuum modulator is mounted next to EGR valve. Clean filter with compressed air. Install filter with coarse side facing upward. Install cap.
- Using a vacuum "T", connect a vacuum gauge in hose between EGR valve and EGR vacuum modulator. To ensure EGR valve is seating, start engine and check idle quality.
- If idle is smooth, go to next step. If idle is rough, disconnect vacuum hose from EGR valve. If idle is smooth, check for problems in EGR vacuum control system. If idle is still rough, EGR valve is not seating. Replace EGR valve.
- Ensure engine coolant is less than 113°F (45°C). Block wheels. Apply parking brake. Start engine and allow it to idle. Firmly depress and hold parking brake pedal down. Shift transmission into "D" position. Slowly depress accelerator pedal, and raise engine speed to 1200-1600 RPM while observing vacuum gauge. There should be no vacuum indicated (no EGR occurs). If any vacuum is indicated, check EGR system components.
- If no vacuum is indicated, warm engine to 122°F (50°C). Again, slowly depress accelerator pedal and raise engine speed to 1200-1600 RPM and observe vacuum gauge. If no vacuum or high vacuum is indicated, check EGR system components. If low vacuum (partial EGR) is indicated, disconnect vacuum gauge.
- Reconnect all vacuum hoses. Disconnect vacuum hose from EGR valve. Apply vacuum directly to EGR valve. If engine runs rough or stalls, system is okay. If engine does not run rough or stall, replace EGR valve.