CHECKING ENGINE IDLE
SPEED AND CO LEVEL

Requirements for All Adjustments:
Engine at operating temperature, l.e.
oil temperature at least 60° C (140° F).
Correct valve clearance.
Engine and ignition in perfect running
condition.
BMW Service Tester connected to the
operating instructions.
Routine checking is not necessary.

1) Engine Idle Speed
Check engine idle speed = 760 ± 40 rpm.
If the nominal value is not reached -
see BMW diagnosing system.
Check the intake system for leaks.

Note:
There is no adjusting screw for
regulation of the engine speed.

2) CO Level
Disconnect oxygen sensor plug. Unscrew
bolts (1). Connect Special Tools
13 0 090 and 13 0 100 on the exhaust
manifold. Check the idle speed CO
level = 0.7 æ 0.5 % by volume. Switch
off the exhaust extraction system for
the time of testing.
Excessive CO Level:
Check fuel injectors, fuel pressure and
coolant temperature sensor.
Insufficient CO Level:
Check hoses and connection for idle
speed control or detect locations of air
leakage.

Important!
The position of air flow sensor
adjusting screw must not be changed,
because this adjustment is the basis
for oxygen sensor and idle speed
control regulation.

Checking Function of Oxygen Sensors
(1178):
Unscrew bolt (1).
Connect Special Tools 13 0 090 and
13 0 100 on the exhaust manifold.
Switch off the exhaust extraction
system for the time of testing.

Disconnect the oxygen sensor plug.
Clamp the vacuum hose leading to the
fuel pressure regulator (not while the
engine is running).
Start the engine - CO level rises.
Connect the oxygen sensor - the CO
level should return to the nominal
value.
Remove hose clamp.