Attention: When the Motronic system is operating, the idle speed is controlled by the electronically controlled idle speed controller.
Turn off all electrical consumers.
Check the air filter element.
Warm up the engine to operating temperature. The oil temperature must be at least 60°C.
Attention: Connect measuring instruments only when the ignition is switched off.
Connect a speed meter to terminals 1 (-) and 15 (+) ignition coils.
Connect a device for measuring CO in the exhaust manifold, to do this, unscrew both plug bolts from the left and right manifolds. At service stations, BMW-130090 gas analyzers with BMW-130100 adapter are used for this.
Disconnect the lambda probe connector on the bulkhead by unscrewing the knurled nut.
Start the engine and leave it to idle.
Check ignition timing.
Check idle speed and CO content. See the table below for set values.
In case of deviations from the specified values, check the tightness of the intake system. To do this, cover with gasoline all the connections of the intake device with a brush. If at the same time briefly increase the engine speed, then air will be sucked in in loose places. Locate and eliminate leaks.
Attention: Do not inhale fuel vapors - poison! Avoid splashing gasoline on hot parts and on the ignition system. Fire hazard!
In case of deviations from the set values of CO content, the following reasons may be: defective nozzles, deviation from the norm of fuel pressure, defective coolant temperature sensor.
If the CO content is low: Check the tightness and tightness of the hoses and connections of the idle speed control system.
Turn off the engine.