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1978-79 Models

  1. With engine at idle, valve must be in closed position. If it is not, lean mixture and rough idle will result. If MCV displays rough idle, it cannot be repaired. Replace MCV.
  2. Increase engine speed rapidly from idle to 2500 RPM, then release. Valve should open. If not, clogged vacuum passage, broken diaphragm or defective valve may be the problem. Replace MCV.
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