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Closing Test (4.2L Engine)

  1. With engine operating at normal operating temperature and at curb idle, manually lift EGR valve diaphragm. This should cause an immediate drop in engine speed and indicate EGR has been properly preventing flow of exhaust gases to intake manifold at idle speed.
  2. If engine speed does not drop, passage between EGR valve and manifold may be plugged. If engine idles rough and is not effected by depressing the diaphragm, fault is in EGR valve or vacuum lines and switches.
  3. If engine idles properly but there is no change in engine speed when valve is opened, exhaust gases are not reaching the combustion chamber. Check for a plugged passage between the EGR valve and the intake manifold.
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