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Home >> Jeep >> 1990 >> Cherokee Laredo, 2D Utility, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests - 4.0L >> Exhaust Gas RECIRCULATION (EGR) System >> EGR Valve Closing Test

EGR Valve Closing Test

  1. With engine at normal operating temperature and curb idle speed, manually depress EGR valve diaphragm. There should be an immediate drop in engine RPM (indicating that EGR valve has been properly preventing flow of exhaust gas to the intake manifold at idle speed). If there is no change in RPM and engine is idling properly, exhaust gases are not reaching combustion chamber. Check for a restricted passage between EGR valve and intake manifold.
  2. If engine idles improperly and RPM is not greatly affected by depressing EGR valve diaphragm, EGR valve is not preventing flow of exhaust gases to intake manifold. There is either a fault in the vacuum hoses, improper hose connection or valve is defective.
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