Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Co-Adjustment Using Test Diode 999 5280
- Connect test diode. Connect test diode green/white wire to test point at right wheel house (connector w/pink wire). Test diode red wire should be connected to battery (+). Connect test meters, Tachometer analyser/stroboscope. Warm-up and run engine at 1500 rpm. Check the idle speed.NOTE: Warm up engine until radiator thermostat opens and then for a further 10 minutes.
Ground blue-white wire to close air control valve. Switch off A/C as applicable. Adjust engine speed w/idle adjustment scre to 700 rpm. Disconnect ground from test point. Engine should increase to 750 +/- 20 rpm. If values are incorrect, check/adjust throttle controls. See THROTTLE VALVE, SWITCH, LINKAGE ADJUSTING
- Check/adjust ignition setting. Idle speed flctuations can affect ignition setting. Make sure that fluctuations are not greater than 25 rpm. If greater, check air control valve hoses for blockages. Ignition setting should be 12°BTDC at idle. Adjust setting by turning distributor body.
- Check CO. Test diode should flash if CO is correct. If test diode remains on = CO is too high (rich air/fuel mixture). If test diode remains off = CO is too low (lean air/fuel mixture).
- Adjusting CO. CO should only be adjusted after all possible faults have been checked/rectified. Remove seal. Turn off engine. Drill two 2mm (0.08 in.) holes in plug. Withdraw plug w/circlip pliers. Start engine. Adjust CO content. CO screw should be turned until test diode starts to flash. Turning adjustment screw, counterclockwise reduces CO and clockwise increases CO. 15 is the adjustment range.
- Seal CO adjustment screw. Always use a new plug. Push plug into position. Disconnect test instruments.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.