5 Series E34 525td (M51) TOUR
VK-23, Löschan
Baugruppe/Group: 11
11 04 96 (111)
weltweit
all countries
12/1996
Troubleshooting of air supply and exhaust re-circulation (AGR)
M41, M51
Situation:
If complaints are received about a lack of power and low top speed, this means that not
enough fuel, or not enough oxygen is entering the cylinders in the combustion cycle. Faults
relating to the "fuel system" are described in the Enclosure to
SI 13 01 92 (568).
The following section only deals with factors/components affecting combustion air.
In broad terms, in addition to leaks, three faults can occur in the air supply system.
1.
Sensors: Inaccurate information from the charge pressure sensor, temperature sensor
or mass air flow sensor, although it has no direct influence on the air supply, can
cause the DDE control unit to misinterpret air conditions.
2.
Charge pressure: Charge pressure can be too high or too low, dependent on engine
speed.
3.
Exhaust re-circulation: The AGR valve fails to close or has a leak. This means that
exhaust gas can be directed into the combustion air in an uncontrolled manner.
As a result of more stringent emission control legislation, diesel engines can be sub-divided
into two groups.
-
Engines with AGR control, EC Level 1
-
Engine with AGR feedback control, EC Level 2
At present, AGR control is available on all M41 engines, all M51 engines in the E34 and
the M51 engine in the E36 up to December 1995.
Note:
The E36/M41 variant, although it only has AGR control satisfies EC Emission Level 2
because of the favourable vehicle weight.
To satisfy the emission levels specified in EC Level 2, M51 engines in the E36 from 1/96,
and all M51 engines in the E39 and E38 are equipped with AGR feedback control.
A clear identifying feature on engines with AGR feedback control, in addition to the use of
a hot-film mass air flow sensor, is the addition of an auxiliary air filter for the electro-
pneumatic pressure converter under the coolant expansion tank.
Effect:
A lack of air leads to a loss of power and a reduction in top speed (Vmax) combined with
"black smoke".
Affected
vehicles:
E36 with M41 and M51; E34, E38 and E39 with M51
Action:
If a customer complaint is received, work through inspection points A-D described below.
Procedure:
A.
Visual inspection of charge air circuit and the exhaust turbo-charger (ATL)
Check components in the charge air circuit for leaks. Traces of oil are additional indicators.
Also check the following:
-
Charge air hoses for signs of damage - ensure they are correctly seated with no leaks
-
If appropriate, check intercooler for signs of mechanical damage (stone chip)
SI Troubleshooting of air supply and exhaust re-circulation (AGR) M41 M51
BMW AG - TIS
23.01.2013 05:52
Issue status (12/2007) Valid only until next DVD is issued
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