1993 Jeep Cherokee
1990-95 ENGINE PERFORMANCE Jeep EGR Function Testing
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
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.