Note: When the Motronic system is operating, the idle speed is controlled by an electronically controlled idle speed controller.
Turn off all electrical consumers.
Check the air filter element.
Warm up the engine to operating temperature. Oil temperature should be at least 60°C.
Attention: Connect measuring instruments only when the ignition is off.
Connect the speed meter to terminals 1 (-) and 15 (+) of the ignition coil.
Connect the CO measuring device to the exhaust manifold by unscrewing both plug bolts from the left and right manifolds. Service stations use BMW-130090 gas analyzers with a BMW-130100 adapter for this purpose.
Disconnect the lambda probe connector on the bulkhead by unscrewing the knurled nut.
Start the engine and let it idle.
Check the ignition timing.
Check the idle speed and CO content. For specified values, see the table below.
If there are deviations from the specified values, check the tightness of the intake system. To do this, use a brush to cover all the joints of the intake device with gasoline. If you briefly increase the engine speed, air will be sucked in at loose places. Localize and eliminate leaks.
Warning: Do not inhale fuel vapors - poison! Do not allow gasoline to splash onto hot parts or the ignition system. Fire hazard!
Deviations from the specified CO content values may be due to the following reasons: defective injectors, deviation from the fuel pressure norm, defective coolant temperature sensor.
If the CO content is low: check the reliability of the fastening and tightness of the hoses and connections of the idle speed control system.
Turn off the engine.