LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> GMC >> 1990 >> Forward Control 3.9 L >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests >> Exhaust Gas RECIRCULATION (EGR) >> System Test
September 30: LEMON manuals is back up on a temporary server! Slowness is possible

System Test

Start and run engine to normal operating temperature. With engine at idle, RPM should drop as EGR valve is opened by pushing up on underside of EGR diaphragm.

CAUTION: Wear gloves when handling EGR valve when it is hot .
scientia non olet · About LEMON Manuals