Note: On models with a catalytic converter, the idle mixture cannot be adjusted, and on models with the Motronic system, the idle speed cannot be adjusted. Before starting, see Chapter 2. On models equipped with Motronic systems, a tachometer and an exhaust gas analyzer will be required to perform the adjustment (CO meter).
Multitec systems
Control
1. If the CO level is not correct (or if there are doubts about the correct operation) always check first that the air filter element is not clogged. Also check that the spark plugs are in good condition with properly adjusted electrode gaps. Check that the engine breather hose and vacuum hoses are not damaged or clogged. Check that there are no leaks in the air inlet line. Check that the throttle body and manifolds are not damaged. Check that the throttle cable is properly adjusted (see Chapter 19). If the engine runs very erratically, check the compression (Section 2A) and be aware that one of the hydraulic tappets may be faulty. Also check that all wiring is correct. The fuel filter should be changed at the recommended intervals and there should be no exhaust system leaks that could affect the operation of the catalytic converter, if equipped.
Adjustment
2. The idle mixture is completely controlled by the ECU and there is no possibility of adjustment. In addition, precise control cannot be performed without the use of Opel equipment in combination with a precisely calibrated exhaust gas analyzer.
3. The only test that shows the effectiveness of the catalytic converter is the measurement of the CO level in the exhaust gas. The meter is connected to the exhaust pipe. Engine speed (without load) - 3000 rpm. If the CO level exceeds the regulated value, Opel equipment must be used to fully check the fuel injection / ignition system. If the sound of a running engine changes when the system is turned off, the damage must be in the converter, which must be replaced.
Motronic systems
Control
4. To check the idle mixture adjustment, the following conditions must be met:
- a) The engine must be warmed up to normal operating temperature
- b) All electrical consumers must be turned off (cooling fan, heater blower, lights, etc.)
- c) Spark plug gaps must be correctly adjusted - see Section 1
- d) Throttle cable play must be properly adjusted - see Chapter 19
- e) The intake air line must be free of leaks and the air filter must be clean
Adjustment
5. Connect the tachometer and exhaust gas analyzer to the vehicle according to the manufacturer's instructions.
6. Start the engine, let it run at 2000 rpm for approximately 30 seconds, then idle. Check that the idle speed is within the limits specified in the Specifications. It is not possible to adjust the idle speed, and if it is outside those specified in Specifications limits, contact your dealer.
7. If the idle speed is correct, check the CO level in the exhaust gas. If its value is outside the limits specified in the Specifications, adjust the CO content with the idle mixture quality adjustment screw in the air flow meter. The screw is capped at the factory.
8. If the cooling fan turns on during the adjustment procedure, stop the adjustment and continue only when the cooling fan turns off.
9. After setting the idle mixture correctly, turn off the engine and disconnect the test equipment.
Simtec systems
10. Adjustment is not possible on these models.
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