Ported EGR System
- Check vacuum hoses for correct routing. Warm engine to normal operating temperature. Set engine speed to fast idle (or high enough to obtain 5 in Hg at EGR valve). Protect finger from heat and place finger beneath EGR valve so diaphragm movement can be felt.
- Disconnect vacuum hose from EGR valve. Diaphragm should move downward (valve closed) and increase in engine RPM should be noticed. Reconnect vacuum hose to EGR valve. Diaphragm should move upward (valve open) and engine speed should decrease by at least 150 RPM.
- If EGR diaphragm does not move during the test, check for vacuum at hose. If vacuum is present, replace EGR valve. If vacuum is not present, check for leaking vacuum hose or plugged carburetor port. If EGR diaphragm moves during the test, but RPM does not change, check for plugged EGR port or passages.
Backpressure EGR Valve
Check vacuum hose routing. Ensure carburetor vacuum port is not plugged. Warm engine to operating temperature. Increase engine speed to 1500-2500 RPM. Ensure EGR valve opens (valve opens slowly on some models). With engine at idle, connect intake manifold vacuum to EGR valve. Engine should run rough or stall. If EGR valve does not open, check for faulty backpressure sensor or EGR valve. If EGR valve opens, but engine RPM does not change, check for clogged EGR passages.
TEST 3
For EGR function testing, see appropriate ENGINE PERFORMANCE section of electronic information product.