Exhaust Gas Recirculation: Testing and Inspection

EGR SYSTEM

1. Connect a suitable tachometer onto engine as per manufacturer's instructions.
2. Disconnect vacuum hose three-way connector from canister and connect a vacuum gauge on to connector between EGR and TVV valves.
3. With engine cold, start engine and check that the vacuum gauge indicates zero at any engine speed.
4. Allow engine to idle and check vacuum gauge reading. With engine idling, vacuum gauge reading obtained should be zero.
5. Increase engine speed to 3500 RPM. Vacuum gauge reading obtained should be 1.9 inches Hg or greater.
6. At 3500 RPM, disconnect vacuum hose from EGR valve. Plug hose. Ensure engine speed increases a few RPMs.
7. Turn ignition switch to OFF position, and push diaphragm plate by hand, then release it. Ensure diaphragm plate returns smoothly to its original position. Valve may be hot. Wear protective gloves, if necessary, before handling valve.

EGR VALVE

1. Check vacuum diaphragm function by applying an outside vacuum source to vacuum supply tube at top of vacuum diaphragm. The diaphragm should not leak down and should move to the full up position at approximately 7 inches Hg vacuum.
2. Check EGR valve diaphragm for cracks. Replace EGR valve, if necessary.
3. Check for damage and carbon deposits around valve or seat. Replace EGR valve, if necessary.

THERMAL VACUUM VALVE (TVV)

1. Place heating portion of thermal vacuum valve into a container of hot water. Heat water above 129°F.
2. Blow air into one of the TVV lines and ensure TVV is open.
3. Cool sensing portion of valve to 95°F, using cool water.
4. Blow air into one of the TVV lines and ensure TVV is closed.
5. If thermal vacuum valve does not operate as specified, replace valve as required.