1. Check the condition of all components of the intake system (hoses, gaskets). Due to the leakage of these components and the ingress of air into the system «suction» the engine idle speed can change so much that even the idle speed stabilization valve cannot stabilize it.
2. Contact a workshop for a troubleshooting printout. A condition for checking the idle speed is a warm engine, as well as a serviceable fuel injection system and ignition system.
3. Disconnect all consumers of electricity from the on-board network. The radiator fan should not be running.
4. Disconnect and plug both crankcase ventilation hoses.
5. Turn off the air conditioner.
6. Move the automatic transmission control lever to the position «N» or «R».
7. Warm up the engine to operating temperature (engine oil temperature must be at least 60°C.
8. Make sure the air filter insert is not dirty.
To measure CO, a gas analyzer must not be connected to the exhaust pipe. For a car enthusiast, an independent CO check is hardly justified, given that it is mandatory during a technical inspection, and besides, the car owner is unlikely to have a gas analyzer at his disposal.
In workshops, CO checks begin only after the so-called basic adjustment has been made using the VAG 1551 device. This means that certain functions automatically adjusted by the electronic control unit are disabled (e.g. lambda regulation). This is done in order to obtain real CO values.
9. Install the gas analyzer in the tube for measuring CO, located in front of the engine compartment. Make sure the gas analyzer has an airtight fit on the tube.
10. Start the engine and let it idle. The gas analyzer should show 0.15-1.0% (2.6L engine) or 0.3-1.2% (2.8L engine).
For 2.8 l engines, the CO content can be corrected with the CO adjustment screw on the intake air mass flow meter.
2.6L engines do not have this option. If the CO content does not reach the nominal values, then the self-diagnosis system usually registers a malfunction and it can be found in the corresponding printout.
In general, if the obtained values of the CO content deviate from the nominal values, the reason for this should be sought in the leakage of the air intake system, as well as the exhaust gas. In addition, you should make sure that the ignition system is functioning properly. One faulty spark plug increases the CO content by 1.5%.
With an increased content of CO:
- - injector leaks
- high fuel pressure
- Faulty coolant temperature sensor.
With a low CO content:
- the system sucks in additional air as a result of leaks.
Attention! Disconnecting the battery deletes the idle speed correction data. It takes some time for the system to recover. Therefore, if after replacing the battery your car behaves differently than usual, you should not panic. After passing a certain distance, the system will restore the necessary data and will work as before.
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