TO #7
Check all parts of the intake system (pipeline, sealing gaskets) for leaks. Unaccounted air can change the idle speed so much that even the idle stabilization distribution valve cannot set it.
Interrogate the fault memory at the workshop. Another fault is possible.
Verification conditions
The conditions for checking the idle speed are correctly adjusted ignition, the engine warmed up to operating temperature, and serviceable injection and ignition systems.
Next, you need to turn off all electrical consumers in the car.
The cooling system fan should not work (4-cylinder engine).
Remove the crankcase ventilation pipe (in a 5-cylinder engine it is located below the distributor), plug the pipe to the intake manifold (the carbon monoxide intake tube plug is suitable).
Pull out the oil dipstick and cover the guide tube hole with a rag.
Tightly close the hose from the throttle body to the fuel evaporative system valve at the top of the thick air intake hose with a clamp or pliers.
Exhaust gas analysis
At home, CO content testing is usually not carried out, since this procedure is mandatory during the annual technical inspection. A special device is needed for this.
In the workshop, the current in the pressure regulator circuit is also measured, because the pressure regulator, like the idle speed stabilization valve, should be in the middle of the standard range within the basic setting. If this is not the case, this means that despite the standard CO indicator, there is a malfunction in the injection system (in most cases, a leak). It should be checked under the same conditions as when regulating the idle speed.
Connect the CO measuring device to the special tube at the front of the engine compartment. Ensure a tight fit.
Disconnect the plug connection to the lambda probe.
Start the engine and let it idle.
The exhaust gas CO test should show 0.2-1.2% CO (4-cylinder engine) or 0.1-1.1% CO (5-cylinder engine).
If necessary, adjust the CO with the adjusting screw.
Remove the plug above the adjusting screw as follows: drill a 2.5 mm diameter hole in the plug. Screw in a 3 mm self-tapping screw and pull out the plug with pliers.
Important: Never press the accelerator pedal while the adjusting key is attached to the adjusting bolt. The key should always be removed.
After each adjustment process, briefly depress the accelerator pedal before reading the CO indicator.
Note: Everything you need to know about the exhaust gas toxicity test, the catalytic converter function test, the lambda probe test and the throttle cable drive can be found in the chapter "Mono-Motronic injection system". When troubleshooting, the lambda probe should be checked using the method, described here.