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How do we fix the PO402 code on our 1997 Mercury Mountaineer?
Vehicle: 1997 Mercury Mountain 5.0

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P0402 EGR excessive

​ For excessive EGR check the vacuum source at idle there should be little to none, if that area is good the EGR pintle is unseated, this can be either from carbon build up to a failed EGR valve, Replacing the EGR should be the best fix

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