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 "suction" into the system, the engine idle speed can change so much that even the idle speed stabilization valve is unable to stabilize it.
2. Contact the workshop to print out the faults. The condition for checking the idle speed is a warm engine, as well as a functioning fuel injection system and ignition system.
3. Disconnect all electrical consumers from the vehicle's electrical system. The radiator fan should not operate.
4. Disconnect and plug both crankcase ventilation hoses.
5. Turn off the air conditioner.
6. Move the automatic transmission control lever to the "N" or "P" position.
7. Warm up the engine to operating temperature (engine oil temperature should be at least 60°C.
8. Make sure the air filter insert is not dirty.
To measure CO, a gas analyzer cannot be connected to the exhaust pipe. For a car owner, independent CO testing is hardly justified, given that it is mandatory during a technical inspection, and in addition, the car owner is unlikely to have a gas analyzer at his disposal.
In workshops, the CO check is only started after the so-called basic adjustment has been performed using the VAG 1551 device. This means that certain functions automatically adjusted by the electronic control unit are switched off (for example, lambda regulation). This is done in order to obtain real CO values.
9. Install the gas analyzer into the CO measuring tube located in the front of the engine compartment. Make sure that the gas analyzer has a tight 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 2.8L engines, the CO content can be adjusted using the CO adjustment screw on the air mass flow meter.
2.6 L engines do not have this option. If the CO content does not reach the nominal values, the self-diagnostic system usually registers a malfunction and it can be found in the corresponding printout.
In general, if the obtained CO content values deviate from the nominal ones, the reason for this should be sought in the leakage of the air intake system, as well as the exhaust gas outlet. In addition, it should be ensured that the ignition system is functioning normally. One faulty spark plug increases the CO content by 1.5%.
With increased CO content:
- - leaky injector seating
- high fuel pressure
- the coolant temperature sensor is faulty.
With reduced CO content:
- the system sucks in additional air due to leaks.
Attention! When the battery is disconnected, the idle speed adjustment data is deleted. The system needs some time to restore them. Therefore, if after replacing the battery your car behaves differently than usual, do not panic. After a certain distance, the system will restore the necessary data and will work in the previous mode.