Honda Civic/CRX/del Sol 1984-1995 Repair Guide

Idle Mixture



See Figures 1 through 5

This procedure requires a propane enrichment kit.

  1. Place the vehicle in the P or N position. Apply the emergency brake and block the drive wheels. Start the engine and warm it up to normal operating temperature. The cooling fan should come on at least once.
  3. Remove the No. 8 vacuum hose (refer to Emission Controls for vacuum diagrams from the intake air control diaphragm and clamp the hose end.
  5. Connect a suitable tachometer to the engine following the manufacturers instructions.
  7. Check the idle speed with all the accessories turned off. Adjust the idle speed by turning the throttle stop screw, if necessary.
  9. Disconnect the air cleaner intake tube from the air duct on the radiator bulkhead.

Click image to see an enlarged view

Fig. Fig. 1: Proper installation of the propane enrichment kit-1984-87 carbureted engine

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Fig. Fig. 2: Graph showing the increase in engine rpm as compared to the increase in propane-1984-87 carbureted engine

  1. Insert the hose from the propane kit into the intake tube approximately 4 in. (102mm).

Be sure that the propane bottle has an adequate supply of gas before going any further with this procedure.

  1. With the engine idling, depress the push button on top of the propane device, then slowly open the propane control valve to obtain the maximum engine speed. The engine speed should increase as the percentage of propane injected goes up.

Open the propane control valve slowly, because a sudden burst of propane may cause the engine to stall.

  1. The engine idle speed should increase as follows:

    1984-88 Civic 1342cc and 1488cc HF engine with manual transmission-100-150 rpm.
    1984-88 Civic 1488cc (except the HF) with manual transmission-75-125 rpm.
    1984-88 Civic 1488cc (except the HF) with automatic transmission-30-70 rpm.


  1. If the engine speed increases according to specifications, remove the propane kit, all test equipment and reconnect all disconnected vacuum hoses. If the engine speed fails to increase as specified, go on with the following steps.
  3. Disconnect the vacuum hose to the fast idle unloader. Pull the throttle cable out of the bracket.