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Ignition Control Thermovalve

  1. With engine cold, start engine and check for vacuum to outer diaphragm of vacuum advance unit. If vacuum is present, go to next step. If vacuum is not present, check vacuum supply to upper fitting of thermovalve on Prelude. On Accord check vacuum supply to thermovalve. If vacuum supply is okay, replace thermovalve. If not, repair as necessary.
  2. Warm engine to operating temperature. Check for vacuum at outer diaphragm of distributor vacuum advance unit. If vacuum is present, replace thermovalve. If vacuum is not present, valve is functioning properly.
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