Attention: When the Motronic system is operating, the idle speed is controlled by the electronically controlled idle speed controller, the CO content is controlled by the lambda probe. The idle speed and CO content are not adjustable. Maintenance check is not required. However, it is advisable to have the DME fault memory interrogated regularly at a BMW workshop.
Examination
Turn off all electrical consumers.
Check the air filter element and if it is very dirty, replace it.
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 the speed meter according to the manufacturer's operating instructions.
Attention: On a six-cylinder engine, it is not allowed to connect a speed meter to terminals 1 (-) and 15 (+) ignition coils, since each spark plug has its own ignition coil. However, roughly the number of revolutions can be determined by the tachometer on the dashboard.
Start the engine and leave it to idle.
Measure the number of revolutions. Setpoint see below.
If the speed does not correspond to the specified value, check the tightness of the intake tract. To do this, start the engine and leave it to idle. Treat all intake tract seals (air mass meter / intake hose, intake manifold flanges) brush dipped in gasoline. With an increase in the number of revolutions, the engine sucks air in loose wetted places. In this case, replace the corresponding seal.
Caution: Do not splash gasoline on hot parts or on the ignition system. Fire hazard! Do not inhale fuel vapor poison!
Connect a device for measuring CO in the exhaust manifold, to do this, unscrew both plug bolts from the left and right manifolds. The illustration shows the engine of models 316i, 318i. -1- bolt-plug of cylinders 1 and 2; -2- plug bolt for cylinders 3 and 4. On a six-cylinder engine, the exhaust manifold is also divided into two parts; the front cap bolt is for cylinders 1-3 and the rear cap bolt is for cylinders 4-6. At service stations, BMW-130090 gas analyzers with BMW-130100 adapter are used for this.
Raise the car.
Unplug connector for lambda probe at gearbox cross member near catalytic converter by unscrewing knurled nut -arrow-.
Check CO content at idle. See the table below for set values.
With an increased CO content, there may be the following reasons: defective nozzles, abnormal 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. Check the tightness of the intake tract as described above.
Turn off the engine.
After that, check the functioning of the lambda probe.
Turn off the engine.
Clamp the vacuum hose at the connection to the fuel pressure regulator -1- with a clamp or clamp. The pressure regulator is located at the end of the fuel tube to which the injectors are connected. The illustration shows the removed fuel pipe with pressure regulator and injectors on a six-cylinder engine.
Start the engine, the CO content increases.
Connect the lambda probe connector. After that, the CO content should return to the given value.
Turn off the engine.
Remove the clamp from the vacuum hose.
Turn off meters.
Install the cap screws with new gaskets into the exhaust manifold.