Volkswagen Cabriolet How-to Adjusting CIS Air/Fuel Mixture & Idle

Start with a complete tune up (if not recently conducted):
• Replace ignition components: spark plugs, cap, rotor, wires (use Bosch ignition parts and use only W7DC or W7DTC plugs)
• Replace air and fuel filters
• Replace injector seals and idle screw O-ring
• Tighten the injector holders; replace the injector holders if needed
• Check for vacuum leaks using carburetor cleaner (spray around hoses, gaskets, injector O-rings); if idle goes up,
leak found (replace faulty part -- use a bit of RTV when replacing gaskets)
• Check your K-Jetronic grounds
• Test your oxygen sensor and replace if need be (page 5)
• Check your throttle switches and idle boost valves
• Check your CIS system and control pressures
• Check your distributor's centrifugal and vacuum advance mechanisms
• Set your timing, if need be (page 6)
"Do not try to correct engine trouble by making simple adjustments to the idle speed or the idle mixture (CO). Changing
these settings without the proper measuring equipment will only be a hindrance when trying to locate the real fault."

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