EGR Gas Flow Test

Use the following procedure to determine if exhaust gas is flowing through the EGR valve. It can also be used to determine if the EGR tube is plugged, or the system passages in the intake or exhaust manifolds are plugged.

This is not to be used as a complete test of the EGR system.

The engine must be started, running, and warmed to operating temperature for this test.

1. Disconnect the rubber hose at the vacuum fitting on the top of the EGR valve.
2. Connect a hand-held vacuum pump to this fitting.
3. Start the engine.
4. Slowly apply 5 inches of vacuum to the fitting on the EGR valve.
5. While applying vacuum, the engine idle speed should drop or the engine may even stall. This is an indication that exhaust gas is flowing through the EGR tube between the intake & exhaust manifolds.
6. If the engine speed did not change, the EGR valve may be defective, the EGR tube may be plugged with carbon, or the passages in the intake and exhaust manifolds may be plugged with carbon.
a. Remove the EGR valve from the engine.
b. Apply vacuum to the fitting and observe the stem of the EGR valve.
^ If the stem is moving, it can be assumed that the EGR valve is functioning correctly. The problem is in either a plugged EGR tube or plugged EGR passages at the intake or exhaust manifolds. Refer to step C.
^ If the stem will not move, replace the EGR valve.

NOTE: The EGR valve, valve control and attaching hoses are serviced as one unit.

c. Remove the EGR tube between the intake and exhaust manifolds. Check and clean the EGR tube and its related openings in the manifolds. Do not attempt to clean the EGR valve. If the valve shows evidence of heavy carbon build-up near the base, replace it.