MOT No. 7
Check all parts of the intake system (piping, gaskets) for tightness. Penetrating unaccounted air can change the idle speed so much that even the idle speed control valve cannot set it.
Interrogate the memory of the fault memory in the workshop. There may be another problem.
Verification conditions
The conditions for checking the idle speed are correctly adjusted ignition, the engine warmed up to operating temperature, as well as serviceable injection and ignition systems.
Next, you need to turn off all consumers of electric current in the car.
Cooling fan should not work (4 cylinder engine).
Remove crankcase breather pipe (in a 5-cylinder engine located below the distributor), plug the pipe to the intake manifold (suitable carbon monoxide suction tube plug).
Pull out the oil dipstick and cover the hole in the guide tube with a cloth.
Tightly close the hose from the throttle body to the valve of the fuel evaporation system at the top of the thick air intake sleeve with a clamp or pliers.
Exhaust Gas Analysis
At home, checking the CO content is usually not carried out, since this procedure is mandatory when passing the annual technical inspection. This requires a special device.
In the workshop, the current in the pressure regulator circuit is additionally measured, because the pressure regulator, like the idle speed stabilization valve, must be in the middle of the standard range within the basic setting. If this is not the case, then this means that despite the standard CO value, there is a malfunction in the injection system (in most cases - leakage). It should be checked under the same conditions as when adjusting the idle speed.
Connect a CO measuring device to a special tube in front of the engine compartment. Ensure tight fit.
Disconnect plug connection to lambda probe.
Start the engine and leave it to idle.
The test for the content of CO in the exhaust gases 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 hole in the plug. Screw in a 3 mm self-tapping screw and pull out the plug with tongs.
Important: at the time when the adjusting key is attached to the adjusting bolt, in no case should you press the accelerator pedal. The key must always be removed.
After each adjustment process, briefly depress the accelerator pedal before reading the CO value.
Note: Everything you need to know about the exhaust gas test, catalytic converter performance test, lambda probe test and cable drive «gas», you will find in the chapter «Mono-Motronic injection system». When troubleshooting, the lambda probe should be checked according to the method described here.
Visitor comments