June 1991
Service Bulletin 24 01 91 (3196)
Subject: Transmisison Failure during Exhaust Emission Testing
Models: All 1984, 1985, 1986 with 4-speed automatic transmission, 1987
635CSi, 735i, and L7.
Situation: There have been reported isolated cases of automatic
transmissions failing during a High Idle Exhaust Emissions Check. The
failures have resulted from a preconditioning procedure where the engine is
held at high rpm for a prolonged period of time. The following applies to
all states which have a High Idle Exhaust Emission Check.
As the internal transmission components experience normal wear over time,
the possibility of transmission damage exists if the vehicle is operated
for
extended periods of time at high rpm in PARK or Neutral. Such operation
does not constitute normal operating conditions. If, in exceptional cases
such as A/C recharging, injector cleaning, charging system tests, or
emissions testing, vehicle operation at high rpm in PARK or Neutral is
required the following setup procedure must be performed prior to beginning
such operations.
Solution: The emissions test must be conducted with the engine at
operating
temperature. If the engine is not at operating temperature prior to
beginning the test, it is recommended that the vehicle be driven for a
short
period of time to bring the engine to operating temperature. DO NOT run
the
vehicle at high idle to achieve operating temperature.
Once the engine has reached operating temperature, the following pretest
procedure must be performed BEFORE testing begins.
Setup Procedure for I/M Emission Test
1. Shift to PARK.
2. Turn engine OFF.
3. Wait at least 30 seconds.
4. Restart engine, LEAVE TRANSMISSION IN PARK.
After the engine is started, DO NOT move the gear shift selector through
the
Forward or Reverse gears before or during the test sequence. DO NOT EXCEED
2000 RPM.
5. Begin emissions test procedure.
6. If the vehicle fails the emission test, some states allow for an
extended pre-conditioning before the repeat test. In this case the
following procedure should be adhered to.
Precondition Procedure
1. Shift into PARK and turn the engine OFF for 30 seconds.
2. Restart engine, LEAVE TRANSMISSION IN PARK.
3. Engine may be preconditioned at a maximum of 2000 RPM for up to 90
seconds, at which time the repeat test must begin.
If the above steps are not followed, serious transmission damage can
result.
Note: Due to the unusual nature of the emissions check, this type of
failure does not take place under normal operating conditions.
i hope this is of help.
mark