System Operation
NOTE:
For testing backpressure type EGR valves, see EGR VALVE REMOVED (BACKPRESSURE TYPE ONLY) in this article.
- Ensure TVS does not allow vacuum to EGR valve with engine coolant temperature below 85-100°F. Start and warm engine. Ported vacuum should be present at EGR valve with engine coolant temperature above 85-100°F.
- Disconnect ported vacuum hose at EGR valve. Disconnect and plug intake manifold vacuum hose on dual diaphragm EGR. On all models, connect an external vacuum source to EGR valve. Start engine. Apply a minimum of 5 in. Hg vacuum to EGR valve. Engine should run rough and/or stall. If rough running and/or stalling does not occur, go to next step.
- Turn off engine. Using external vacuum source, apply 5-7 in. Hg vacuum to EGR valve. Using a gloved finger beneath EGR diaphragm, ensure diaphragm moves up when vacuum is applied. If EGR diaphragm does not move, replace EGR valve.
- If EGR diaphragm does move, remove EGR valve and check for carbon deposits blocking exhaust flow. Clean carbon deposits (if necessary) and install EGR valve using a new base gasket.