Idle Speed/Timing/CO - Checking Adjusting

Idle Speed/Ignition Timing/OXS-Duty Cycle (CO value), Checking/Adjusting
(1983 Rabbit Carburetor)

Work Sequence

Test conditions:

^ oxygen sensor connected

^ engine oil temperature minimum 8O° C (176° F). Radiator fan must come on at least once

^ all electrical consumers switched OFF (radiator fan must not be running while adjusting)

^ transmission in neutral





- connect tester according to manufacturer's instructions

Note:
TDC sending unit must fit snug into transmission housing

- remove PCV valve from valve cover

- remove cap from CO probe receptacle and connect CO tester

- disconnect both wire plugs at idle stabilizer and connect them together. Check connector plug terminals for good connection

- check idle speed

^ 620-900 rpm





- if out of specification, adjust to 820-900 rpm by turning screw "A" on throttle lever(see illustration)

- disconnect vacuum advance and vacuum retard hoses at distributor and plug hoses

- check timing and adjust if necessary
^ 7.5° +/- 1° BTDC

- reconnect vacuum retard hose at distributor

- readjust idle speed if necessary

- turn ignition OFF

- disconnect dwell lead on tester from ignition coil terminal 1 and connect to oxygen sensor test connection (blue/white wire) on strut tower using adaptor US 1112

- remove test leads from spark plug wire (cylinder 1) and TDC sending unit

- press in % button on tester

- start engine

- check duty cycle and CO%

^ OXS duty cycle must be 25%-45% (reading must fluctuate)

^ CO must be less than 1.5%

- if duty cycle or CO% out of limits, remove carburetor





- remove tamper-proof plug (see arrow in illustration) from idle mixture screw

- reinstall carburetor

- turn idle mixture screw to adjust duty cycle.

Turning screw clockwise, lowers duty cycle reading; turning counterclockwise, raises reading

^ 35 +/- 10% duty cycle (reading fluctuating)

^ less than 1.5% CO

- turn engine OFF

- install new tamper-proof plug

- readjust idle speed if necessary

- reconnect vacuum advance hose at distributor

- reconnect idle stabilizer

- reinstall PCV valve to valve cover

- remove CO meter and reattach cap to probe receptacle