1991 BMW 5 SERIES Transmission automatic

the crankshaft flange (see illustration). Be
careful - the flywheel is heavy.
5To refit the flywheel/driveplate on the
crankshaft, use a liquid thread-locking
compound on the bolts, and tighten them
gradually, using a criss-cross pattern, to the
torque listed in this Chapter’s Specifications.
6The remainder of refitting is the reverse of
removal.
16 Crankshaft rear oil seal-
renewal
3
1Remove the flywheel or driveplate (see
Section 15).
2Remove the bolts and/or nuts attaching the
seal retainer to the engine block. Be sure to
remove the two bolts (from underneath)
connecting the rear of the sump to the bottom
of the seal retainer (see illustration).
3Run a sharp, thin knife between the sump
gasket and the seal retainer, cutting the
retainer free from the gasket. Be very careful
not to damage the gasket, and keep it clean
so you can re-use it.
4Break the seal retainer-to-block gasket seal
by tapping the retainer with a plastic mallet or
block of wood and hammer. Do not prise
between the retainer and the engine block, as
damage to the gasket sealing surfaces will
result.
5Using a scraper, remove all traces of old
gasket material from the sealing surfaces of
the retainer and engine block. Gasket removal
solvents are available at car accessory shops,
and may prove helpful. After all gasket
material has been removed, the gasket
surfaces can be degreased by wiping them
with a rag dampened with a suitable solvent.
Caution: Be very careful not to
scratch or gouge the delicate
aluminium surfaces. Also, do not
damage the sump gasket, and
keep it clean.
6Support the retainer on two blocks of
wood, and drive out the seal from behind with
a hammer and screwdriver (see illustration).Be very careful not to damage the seal bore in
the process.
7Coat the outside diameter and lip of the
new seal with multi-purpose grease, and drive
the seal into the retainer with a hammer and a
block of wood (see illustration).
8Apply a film of RTV-type gasket sealant to
the surface of the sump gasket that mates with
the seal retainer. Apply extra beads of RTV
sealant to the edges where the gasket meets
the engine block. Note:If the sump gasket is
damaged, instead of fitting a whole new
gasket, you might try trimming the rear portion
of the gasket off at the point where it meets the
engine block, then trim off the rear portion of a
new sump gasket so it’s exactly the same size.
Cover the exposed inside area of the sump
with a rag, then clean all traces of old gasket
material off the area where the gasket was
removed. Attach the new gasket piece to the
sump with contact-cement-type gasket
adhesive, then apply RTV-type sealant as
described at the beginning of this paragraph.
9Coat both sides of the new retainer gasket
with RTV-type gasket sealant, then attach the
gasket to the seal retainer. Fit the seal retainer
to the rear of the engine, then refit the bolts
and tighten them evenly to the torque listed in
this Chapter’s Specifications. Work from bolt-
to-bolt in a criss-cross pattern to be sure
they’re tightened evenly.Note 1:Tighten the
retainer-to-block bolts first, then tighten the
sump-to-retainer bolts.Note 2:After applying
RTV-type sealant, reassembly must becompleted in about 10 minutes so the RTV
won’t prematurely harden.
10Refit the flywheel/driveplate (see Sec-
tion 15).
11Refit the transmission (on vehicles with
manual transmission, see Chapter 7A; on
vehicles with automatic transmission, see
Chapter 7B).
17 Engine mountings-
check and renewal
1
1Engine mountings seldom require attention,
but broken or deteriorated mountings should
be renewed immediately, or the added strain
placed on the driveline components may
cause damage or wear.
Check
2During the check, the engine must be
raised slightly to remove its weight from the
mounts.
3Raise the vehicle and support it securely on
axle stands, then position a jack under the
engine sump. Place a large block of wood
between the jack head and the sump, then
carefully raise the engine just enough to take
its weight off the mounts.
Warning: DO NOT place any part
of your body under the engine
when it’s supported only by a
jack!
In-car engine repair procedures 2A•19
16.6 After removing the retainer from the
block, support it on two wood blocks, and
drive out the old seal with a punch and
hammer16.2 Remove the six bolts from the rear of
the block and the two from underneath at
the sump15.4 Using a socket and ratchet, remove
the eight bolts that hold the flywheel/
driveplate to the crankshaft flange - prevent
the flywheel/driveplate from turning by
locking the ring gear with a lever
17.4 As engine mountings wear or age,
they should be inspected for cracking or
separation from their metal plates
16.7 Drive the new seal into the retainer
with a block of wood, or a section of pipe,
if you have one large enough - make sure
the seal enters the retainer bore squarely
2A

detach them. Pieces of masking tape with
numbers or letters written on them work well
(see illustration).
6Label and detach all coolant hoses from the
engine (see Chapter 3).
7Remove the cooling fan, shroud and
radiator (see Chapter 3). Note:On the M40
engine, it is only necessary to remove the
cooling fan and shroud; however, prevent
damage to the radiator by covering it with a
piece of wood or cardboard.
8Remove the drivebelts (see Chapter 1).
9Disconnect the fuel lines from the fuel rail
(see Chapter 4).
Warning: Fuel is extremely
flammable, so take extra
precautions when you work on
any part of the fuel system. Don’t
smoke, or allow open flames or bare light
bulbs, near the work area, and don’t work
in a garage where a natural gas-type
appliance (such as a water heater or
clothes dryer) with a pilot light is present.
If you spill any fuel on your skin, rinse it off
immediately with soap and water. When
you perform any kind of work on the fuel
system, wear safety glasses, and have a
fire extinguisher on hand.
10Disconnect the accelerator cable (see
Chapter 4) and kickdown linkage/speed
control cable (see Chapter 7B), if applicable,
from the engine.
11Where fitted, unbolt the power steering
pump (see Chapter 10). Leave the lines/hoses
attached, and make sure the pump is kept in
an upright position in the engine compartment
(use wire or rope to restrain it out of the way).
12On air-conditioned models, unbolt the
compressor (see Chapter 3) and set it aside,
or tie it up out of the way. Do not disconnect
the hoses.
13Drain the engine oil (see Chapter 1) and
remove the filter. Remove the engine splash
guard from under the engine.
14Remove the starter motor (see Chapter 5).15Remove the alternator (see Chapter 5).
This is not essential on all models, but it is a
good idea in any case to avoid accidental
damage.
16Unbolt the exhaust system from the
engine (see Chapter 4).
17If you’re working on a vehicle with an
automatic transmission, remove the torque
converter-to-driveplate fasteners (see
Chapter 7B). On the M40 engine, unbolt the
automatic transmission fluid coolant pipes
from the sump.
18Support the transmission with a jack.
Position a block of wood between them, to
prevent damage to the transmission. Special
transmission jacks with safety chains are
available - use one if possible.
19Attach an engine sling or a length of chain
to the lifting brackets on the engine. If the
brackets have been removed, the chain can
be bolted directly to the intake manifold studs,
but place a flat washer between the chain and
the nut, and tighten the nut all the way up to
the chain, to avoid the possibility of the studs
bending.
20Roll the hoist into position and connect
the sling to it. Take up the slack in the sling or
chain, but don’t lift the engine.
Warning: DO NOT place any part
of your body under the engine
when it’s supported only by a
hoist or other lifting device.
21On M10, M20 and M30 engines, remove
the transmission rear crossmember, and
slightly lower the rear of the transmission.
22Remove the transmission-to-engine block
bolts using a Torx socket. Note:The bolts
holding the bellhousing to the engine block
will require a swivel at the socket, and a very
long extension going back towards the
transmission.
23Remove the engine mounting-to-frame
bracket nuts. On the M40 engine, unbolt the
dampers from the mountings.
24Recheck to be sure nothing is still
connecting the engine to the transmission or
vehicle. Disconnect anything still remaining.
25Raise the engine slightly. Carefully work it
forwards to separate it from the transmission.
If you’re working on a vehicle with an
automatic transmission, you may find the
torque converter comes forward with theengine. If it stays with the transmission, leave
it, but you may find it easier to let it come
forward until it can be grasped easier and be
pulled from the crankshaft. Note:When
refitting the torque converter to the
transmission before the engine is refitted, be
sure to renew the transmission front pump
seal, which will probably be damaged when
the converter comes out with the engine.
Either method is acceptable, but be prepared
for some fluid to leak from the torque
converter if it comes out of the transmission. If
you’re working on a vehicle with a manual
transmission, draw the engine forwards until
the input shaft is completely disengaged from
the clutch. Slowly raise the engine out of the
engine compartment. Check carefully to make
sure everything is disconnected.
26Remove the flywheel/driveplate (and
where applicable, the engine rear plate), and
mount the engine on an engine stand (see
illustration). Do not turn the M40 engine
upside-down (see Cautionin Section 4).
Refitting
27Check the engine and transmission
mountings. If they’re worn or damaged, renew
them.
28Refit the flywheel or driveplate (see
Chapter 2A). If you’re working on a manual
transmission vehicle, refit the clutch and
pressure plate (see Chapter 7A). Now is a
good time to fit a new clutch.
29If the torque converter came out with the
engine during removal, carefully refit the
converter into the transmission before the
engine is lowered into the vehicle.
30Carefully lower the engine into the engine
compartment - make sure the engine
mountings line up.
31If you’re working on an automatic
transmission vehicle, guide the torque
converter onto the crankshaft following the
procedure outlined in Chapter 7B.
32If you’re working on a manual
transmission vehicle, apply a dab of high-
melting-point grease to the input shaft, and
guide it into the clutch and crankshaft pilot
bearing until the bellhousing is flush with the
engine block.. Do not allow the weight of the
engine to hang on the input shaft.
33Refit the transmission-to-engine bolts,
and tighten them securely.
Caution: DO NOT use the bolts to
force the transmission and
engine together.
34Refit the remaining components in the
reverse order of removal.
35Add coolant, oil, power steering and
transmission fluid as needed.
2B•6 General engine overhaul procedures
5.26 Removing the engine rear plate -
M40 engine5.5 Label each wire before unplugging the
connector
If there’s any possibility of
confusion, make a sketch of
the engine compartment and
clearly label the lines, hoses
and wires.
It may be necessary to rock
the engine slightly, or to turn
the crankshaft, to allow the
input shaft splines to mate
with the clutch plate

12If the outer surface of the fitting that
mates with the hose is deteriorated (corroded,
pitted, etc.), it may be damaged further by
hose removal. If it is, a new thermostat
housing cover will be required.
13Remove the bolts and detach the housing
cover. If the cover is stuck, tap it with a soft-
faced hammer to jar it loose. Be prepared for
some coolant to spill as the gasket seal is
broken.
14Note how it’s fitted, then remove the
thermostat.
15Stuff a rag into the engine opening, then
remove all traces of old gasket material (if the
gasket is paper type). Otherwise, remove the
rubber O-ring (see illustration)and sealant
from the housing and cover with a gasket
scraper. Remove the rag from the opening
and clean the gasket mating surfaces.
16Fit the new thermostat and gasket in the
housing. Make sure the correct end faces out
- the spring end is normally directed towards
the engine.
17Refit the cover and bolts. Tighten the
bolts to the torque listed in this Chapter’s
Specifications.
M40 engines
18Remove the cooling fan and timing belt
upper cover.
19Unscrew the hose clamp and detach thebottom hose from the elbow on the front of
the cylinder head.
20Unbolt the elbow from the cylinder head.
Note the fitted position of the thermostat, then
remove it (see illustrations). Remove the
rubber O-ring; a new one will be needed for
reassembly.
21Locate the thermostat in the cylinder head
in the same position as noted during removal
(arrow pointing upwards).
22Press a new O-ring in the groove, and
locate the elbow on the cylinder head. Tighten
the bolts.
23Connect the bottom hose to the elbow,
and tighten the hose clamp.
24Refit the upper timing belt cover and
cooling fan.
All models
25Refill the cooling system (see Chapter 1).
26Connect the battery negative cable.
27Start the engine and allow it to reach
normal operating temperature, then check for
leaks and proper thermostat operation (as
described earlier in this Section).
4 Radiator-
removal and refitting
1
Warning: Wait until the engine is
completely cool before beginning
this procedure.Note: If the radiator is being removed because
it is leaking, note that minor leaks can often be
repaired without removing the radiator, using
a radiator sealant.
Caution: If the radio in your
vehicle is equipped with an anti-
theft system, make sure you
have the correct activation code
before disconnecting the battery.
Note: If, after connecting the battery, the
wrong language appears on the instrument
panel display, refer to page 0-7 for the
language resetting procedure.
Removal
1Disconnect the battery negative cable.
2Drain the cooling system (see Chapter 1). If
the coolant is relatively new, or in good
condition, save it and re-use it.
3Loosen the hose clamps, then detach the
hoses from the radiator (see illustrations). If
they’re stuck, grasp each hose near the end
with a pair of water pump pliers, twist gently
to break the seal, then pull off - be careful not
to distort or break the radiator outlets! If the
hoses are old or deteriorated, cut them off
and refit new ones.
4On M20 and M30 engines, disconnect the
reservoir hose from the radiator filler neck.
5Remove the screws or plastic fasteners that
attach the shroud to the radiator, and slide the
shroud towards the engine (see illustration).
On some engines it is possible to completely
remove the shroud.
6If the vehicle has automatic transmission,
Cooling, heating and air conditioning systems 3•3
3.20b Removing the thermostat
(M40 engine)3.20a Removing the elbow from the
cylinder head (M40 engine)3.15 On M20 and M30 engine models,
after the housing and thermostat have
been removed, take the O-ring out of the
housing and clean the recess in the
housing to be sure of a good seal upon
reassembly
4.5 Plastic fastener retaining the radiator
shroud on some engines4.3b Bottom hose connection to the
radiator4.3a Disconnecting the top hose from the
radiator
3

disconnect the fluid cooler lines from the
radiator. Use a drip tray to catch spilled fluid.
Plug the fluid cooler lines and fittings.
7Disconnect the coolant sensors located on
the radiator (see illustration). The thermo-
statically-controlled switches for high- and
low-speed operation of the auxiliary fan are
located in the radiator tanks, in various
locations depending on engine and model.
8Remove the radiator mounting bolt(s). The
mountings are either on the top or sides of the
radiator (see illustration).
9Carefully lift out the radiator from the
bottom mountings, taking care not to damage
the cooling fins. Don’t spill coolant on the
vehicle, or scratch the paint.
10With the radiator removed, it can be
inspected for leaks and damage. If it needs
repair, have a specialist perform the work, as
special techniques are required.
11Flies and dirt can be removed from the
radiator with compressed air and a soft brush.
Don’t bend the cooling fins as this is done.
12Check the radiator mountings for
deterioration, and renew if necessary (see
illustration).
Refitting
13Refitting is the reverse of the removal
procedure.
14After refitting, fill the cooling system with
the proper mixture of antifreeze and water.
Refer to Chapter 1 if necessary.15Start the engine and check for leaks.
Allow the engine to reach normal operating
temperature, indicated by the upper radiator
hose becoming hot. Recheck the coolant
level, and add more if required.
16If you’re working on an automatic
transmission model, check and add
transmission fluid as needed.
5 Engine cooling fan(s) and
clutch- check, removal and
refitting
1
Warning: To avoid possible injury
or damage, DO NOT operate the
engine with a damaged fan. Do
not attempt to repair fan blades -
fit a new fan. Also, the electric auxiliary fan
in front of the radiator or air conditioning
condenser can come on without the
engine running or ignition being on. It is
controlled by the coolant temperature of
the thermo-switches located in the
radiator.
Check
Electric auxiliary fan
Note: This fan on most models is controlled
by two thermo-switches placed in the radiator:
one for low-speed/low-temperature operation,
and one for high-speed/high-temperature
operation. Each switch comes on at a different
coolant temperature (refer to the Specifica-
tions at the beginning of this Chapter).
1The thermostatically-controlled switches for
high- and low-speed operation of the auxiliary
fan are fitted in various locations in the
radiator (see illustration 4.7), depending on
engine or model. Two single switches, or one
dual switch, may be fitted.
2Insert a small screwdriver into the
connector to lift the lock tab, and unplug the
fan wire harness.
3To test the fan motor, unplug the electrical
connector at the motor, and use jumper wires
to connect the fan directly to the battery. If the
fan doesn’t work when connected directly to
the battery, the motor is proved faulty, and
must be renewed. If the fan works, there’s agood chance the switch is malfunctioning. To
more accurately diagnose the problem, follow
the steps that apply to your model. Note: Spin
the auxiliary fan motor by hand, to check that
the motor or fan isn’t binding. Make sure,
however, that the engine is sufficiently cool
that there is no danger of the fan cutting-in on
its own when this is done.
4To test the low-speed and high-speed
circuits, disconnect the electrical connector
from one of the fan switches, and bridge the
terminals of the switch’s electrical connector
with a short piece of wire. The fan should run
at low or high speed, depending on which
switch has been disconnected. On some
models the ignition must be on before the fan
will run.
5Repeat the test at the other switch so that
both high and low speeds are tested.
6If the low-speed and high-speed circuits
are OK, but there has been a problem with the
fan not operating correctly in service, renew
the switch (or switches). To remove a switch,
drain the coolant below the level of the switch
(see Chapter 1), then unscrew the switch and
screw in the new one. Refill the system with
coolant.
7If the switches are satisfactory, but the
motor still does not operate, the problem lies
in the fuse, the relay, the wiring which
connects the components (or the fan motor
itself). Carefully check the fuse, relay, all
wiring and connections. See Chapter 12 for
more information on how to carry out these
checks.
Mechanical fan with viscous clutch
8Disconnect the battery negative cable, and
rock the fan back and forth by hand to check
for excessive bearing play.
Caution: If the radio in your
vehicle is equipped with an anti-
theft system, make sure you
have the correct activation code
before disconnecting the battery.
Note: If, after connecting the battery, the
wrong language appears on the instrument
panel display, refer to page 0-7 for the
language resetting procedure.
9With the engine cold, turn the fan blades by
hand. The fan should turn with slight
resistance.
10Visually inspect for substantial fluid
leakage from the fan clutch assembly. If
problems are noted, renew the fan clutch
assembly.
11With the engine completely warmed up,
turn off the ignition switch and disconnect the
battery negative cable. Turn the fan by hand.
Heavier resistance should be evident. If the
fan turns easily, a new fan clutch may be
needed.
Removal and refitting
Electric auxiliary fan
12Disconnect the battery negative cable.
13To remove the auxiliary fan follow the
procedure that applies to your vehicle.
3•4 Cooling, heating and air conditioning systems
4.12 When the radiator is out, the radiator
mountings can be inspected - check for
signs of deterioration, and renew them, if
needed
4.8 The radiator is bolted to the front
panel at either the sides or the top of the
radiator4.7 Sensors that control the high- and
low-speed operation of the auxiliary
cooling fan are located in various places in
the radiator tanks

Caution: If the radio in your
vehicle is equipped with an anti-
theft system, make sure you
have the correct activation code before
disconnecting the battery. Refer to the
information on page 0-7 at the front of this
manual before detaching the cable.
Note: If, after connecting the battery, the
wrong language appears on the instrument
panel display, refer to page 0-7 for the
language resetting procedure.
8Loosen the cable adjuster locknuts, and
detach the cable from its support bracket
located on the intake manifold (see
illustration).
9Pinch the plastic retainer with a pair of
needle-nose pliers, and push it out of the
bracket (see illustration).10Pull the cable down through the slot and
away from the bracket (see illustrations).
11Working from underneath the driver’s side
of the facia, reach up and detach the
accelerator cable from the top of the pedal.
12Pull the cable through the bulkhead, from
the engine compartment side.
13Refitting is the reverse of removal. Adjust
the cable as described earlier.
10 Carburettor-
general information
1Early models are fitted with a Solex 2B4
carburettor, and later models are fitted with a
Solex 2BE carburettor. Both carburettors are
of downdraught, two-stage type. The first
stage is operated mechanically by the
accelerator pedal, and the second stage by
vacuum control.
2Each stage has its own float chamber, float
assembly and needle valve, designed to
reduce the effects of braking and centrifugal
forces.
3On the 2B4 version, the primary stage
choke valve is operated by an automatic
choke (a bi-metal spring which is electrically
heated) during the warm-up period. Warm-up
enrichment is also provided by a coolant-
operated thermal valve and air temperature-
controlled flow valve.
4On the 2BE version, an electronic controlunit is used to automatically adjust the
carburettor settings during warm-up and
normal temperature operation. The control
unit is located beneath the right-hand side of
the facia.
11 Carburettor-
removal and refitting
2
Removal
1Remove the air cleaner as described in
Section 8.
2Disconnect the accelerator cable from the
carburettor with reference to Section 9.
3On automatic transmission models,
disconnect the kickdown cable.
4Disconnect the wiring from the carburettor,
noting the location of each wire.
5Remove the screw, and disconnect the
earth cable from the throttle positioner
bracket (see illustration).
6Disconnect the vacuum hoses, noting that
the hose with the white tracer is located on
the white plastic ‘T’ piece, and the distributor
vacuum hoses are located on the side of the
carburettor (see illustration).
7On the 2B4 carburettor, disconnect and
plug the coolant hoses from the TM (thermal
starter) valve.
8Disconnect the fuel supply hose (see
illustration).
4•10 Fuel and exhaust systems
11.8 Disconnect the fuel supply hose
(arrowed)11.6 Note the locations of the carburettor
vacuum hoses (arrowed) before
disconnecting them11.5 Remove the screw, and disconnect
the carburettor earth cable (arrowed)
9.10b After the cable is off the throttle
valve assembly, remove the plastic
retainer from the cable
9.10a Rotate the throttle valve and remove
the cable end from the slotted portion of
the valve9.9 Pinch the plastic retainer, and push it
through the bracket recess on the throttle
valve9.8 Push the rubber grommet from the
rear, and separate the cable from the
bracket

2L-Jetronic systems are equipped with a
separate idle speed control unit (computer)
located under the facia. The idle air stabiliser
valve has an adjusting screw. Early models
are equipped with plastic valves, but they still
can be adjusted by removing the hose and
inserting a very thin screwdriver inside.
3Early Motronic systems are also equipped
with a separate idle speed control unit
(computer) located under the facia. The idle
air stabiliser valve has an adjusting screw.
4On later Motronic systems, the idle air
stabiliser valve is ECU-controlled, and no
provision is made for adjustment.
Preliminary check
5Before performing any checks on the idle
air stabiliser valve, make sure these criteria
are met:
a) The engine must be at operating
temperature (60ºC)
b) Turn off all electrical accessories (air
conditioning, heater controls, headlights,
auxiliary cooling fan, etc)
c) The throttle position sensor must be
operating correctly (see Chapter 6)
d) There must not be any exhaust leaks
e) There must not be any vacuum leaks
f) Where fitted, the oxygen sensor must be
operating properly (see Chapter 6)
6Connect a tachometer in accordance with
the manufacturer’s instructions.
Caution: The ignition must be
switched off before making any
electrical connections.
7The idle air stabiliser valve operates
continuously when the ignition is on. Start the
engine and make sure the valve is vibrating
and humming slightly.
L-Jetronic system
Check
8With the engine running, disconnect the
electrical connector from the valve. The idle
speed should increase to about 2,000 rpm.
9If the idle speed does not increase, turn the
engine off. Using an ohmmeter, check the
resistance across the terminals of the valve(see illustration). It should be 9 to 10 ohms
with the ambient air temperature at about
20º C.
10Using a pair of jumper wires, apply battery
voltage to the valve, and confirm that the
valve closes tightly. When the voltage is
removed, the valve should re-open.
11If the idle air stabiliser valve fails any of
the tests, renew it.
12If the idle air stabiliser valve passes the
tests, check the control current.
13Unplug the electrical connector from the
valve. Using a jumper wire, connect one
terminal of the electrical connector to one of
the terminals on the valve, Connect an
ammeter (0 to 1000 mA range) between the
other terminal on the electrical connector and
the remaining terminal on the valve. Start the
engine and allow it to idle. With the engine
running, the current reading should be
between 400 and 500 mA. Adjust the valve if
the current reading is not as specified (see
paragraph 15). Note: The idle air stabiliser
current will fluctuate between 400 and
1100 mA if the engine is too cold, if the
coolant temperature sensor is faulty, if the idle
speed needs to be adjusted, if there is an
engine vacuum leak or if electrical accessories
are on.
14If there is no current reading, have the idle
speed control unit diagnosed by a BMW
dealer or other specialist. Note: The idle air
stabiliser control unit (located under the facia)
can develop an electrical connector problem
that intermittently turns the valve on and off.
Check the connector very carefully before
fitting any new parts. Sometimes, a new
control unit will only fix the problem
temporarily.
Adjustment
15With the ignition switched off, connect a
tachometer in accordance with the equipment
manufacturer’s instructions.
16Make sure the ignition timing is correct
(see Chapter 5).
17Connect an ammeter to the valve (see
paragraph 13).
18With the engine running, the current
reading should be 450 to 470 mA at 850 to900 rpm (manual transmission), or 460 to
480 mA at 850 to 900 rpm (automatic
transmission).
19If the control current is not correct, turn
the adjusting screw until it is within the correct
range (see illustration). Note: On metal-type
valves, the adjusting screw is mounted
externally. On plastic-type valves, the
adjustment screw is inside, and can be
reached by removing the hose at the end of
the valve.
Motronic systems
Check
Note:There are two types of idle air stabiliser
valve on these systems; early models usually
have a two-wire valve, while later models are
equipped with a three-wire valve.
20With the engine running, disconnect the
electrical connector from the valve. The idle
speed should increase to about 2000 rpm.
21If the idle speed does not increase:
a) Two-wire valve - Using a pair of jumper
wires, apply battery voltage to the valve,
and confirm that the valve closes tightly.
When the voltage is removed, the valve
should re-open. Also, check the
resistance of the valve (see illus-
tration 21.9). The resistance should be
about 9 or 10 ohms.
b) Three-wire valve - Turn the engine off and
unplug the electrical connector from the
valve. Using an ohmmeter, check the
resistance on the two outer terminals of
the valve. (see illustration). It should be
about 40 ohms. Check the resistance on
the centre and outside terminals of the
valve. They should both be about
20 ohms.
22If the idle air stabiliser valve fails any of
the tests, renew it.
23If the idle air stabiliser valve tests are all
correct, check the control current (two-wire
valve) or the voltage (three-wire valve) as
follows.
24On two-wire valves, connect an ammeter
(0 to 1000 mA range) as described in
paragraph 13. Start the engine, and allow it to
idle. With the engine running, the current
Fuel and exhaust systems 4•19
21.21 Check the idle air stabiliser valve
resistance on the two outer terminals on
later Motronic systems - it should be about
40 ohms21.19 Location of the adjustment screw on
the metal-type idle air stabiliser valve
(L-Jetronic system)21.9 Check the resistance of the idle air
stabiliser valve - it should typically be 9 to
10 ohms (L-Jetronic system)
4

7 Ignition timing (TCI system)-
check and adjustment
4
Warning: Keep hands, equipment
and wires well clear of the
viscous cooling fan during
adjustment of the ignition timing.
Note:This Section describes the procedure
for checking and adjusting the ignition timing
on engines fitted with the TCI system. On
engines fitted with the Motronic engine
management system, the ignition timing is
controlled by the electronic control unit, and
no adjustment is possible. The timing can be
checked using the following procedure, but no
ignition timing values were available at the
time of writing. If the timing is thought to be
incorrect, refer to a BMW dealer.
1Some special tools are required for this
procedure (see illustration). The engine must
be at normal operating temperature, and the
air conditioning (where fitted) must be
switched off. Make sure the idle speed is
correct.
2Apply the handbrake, and chock the wheels
to prevent movement of the vehicle. The
transmission must be in neutral (manual) or
Park (automatic).
3The timing marks are located on the engine
flywheel (viewed through the timing checkhole in the bellhousing) and/or on the vibration
damper on the front of the engine.
4Where applicable, disconnect the vacuum
hose from the distributor vacuum advance
unit.
5Connect a tachometer and timing light
according to the equipment manufacturer’s
instructions (an inductive pick-up timing light
is preferred). Generally, the power leads for
the timing light are attached to the battery
terminals, and the pick-up lead is attached to
the No 1 spark plug HT lead. The No 1 spark
plug is the one at the front of the engine.
Caution: If an inductive pick-up
timing light isn’t available, don’t
puncture the spark plug HT lead
to attach the timing light pick-up
lead. Instead, use an adapter between the
spark plug and HT lead. If the insulation on
the HT lead is damaged, the secondary
voltage will jump to earth at the damaged
point, and the engine will misfire.
Note:On some models, a TDC transmitter is
fitted for checking the ignition system.
However, a special BMW tester must be
connected to the diagnostic socket to use it,
so unless the special tester is available, a
conventional timing light should be used. The
ignition timing mark may be on the vibration
damper, but if not, normally the TDC mark will
be. If the timing light is of the adjustable delay
type, then the ignition timing may be
determined by zeroing the adjustment, then
turning the adjustment until the TDC marks are
aligned, and then reading off the amount of
advance from the timing light. If a standard
timing light is being used, make a mark on the
vibration damper in accordance with the
specified advance, using the following formula
to calculate the distance from the TDC mark
to the timing mark:
Distance = 2Pr x advance
360
where P = 3.142
r = radius of vibration damper
advance = specified advance
BTDC in degrees
6With the ignition off, loosen the distributor
clamp nut just enough to allow the distributor
to pivot without any slipping.7Make sure the timing light wires are routed
away from the drivebelts and fan, then start
the engine.
8Raise the engine rpm to the specified
speed, and then point the flashing timing light
at the timing marks - be very careful of moving
engine components.
9The mark on the flywheel or vibration
damper will appear stationary. If it’s aligned
with the specified point on the bellhousing or
engine front cover, the ignition timing is
correct (see illustrations).
10If the marks aren’t aligned, adjustment is
required. Turn the distributor very slowly until
the marks are aligned, taking care not to
touch the HT leads.
11Tighten the nut on the distributor clamp,
and recheck the timing.
12Switch off the engine, and remove the
timing light and tachometer. Reconnect the
vacuum hose where applicable.
8 Distributor-
removal and refitting
4
TCI system
Removal
1After carefully marking them for position,
remove the coil HT lead and spark plug HT
leads from the distributor cap (see Chapter 1).
2Remove No 1 spark plug (the one nearest
you when you are standing in front of the
engine).
3Manually rotate the engine to Top Dead
Centre (TDC) on the compression stroke for
No 1 piston (see Chapter 2A)
4Carefully mark the vacuum hoses, if more
than one is present on your distributor.
5Disconnect the vacuum hose(s).
6Disconnect the primary circuit wires from
the distributor.
7Mark the relationship of the rotor tip to the
distributor housing (see illustration). Also
mark the relationship of the distributor
housing to the engine.
5•4 Engine electrical systems
7.1 Tools for checking and adjusting the
ignition timing
1Vacuum plugs- Vacuum hoses will, in
most cases, have to be disconnected and
plugged. Moulded plugs in various shapes
and sizes can be used for this, if wished
2Inductive pick-up timing light- Flashes a
bright, concentrated beam of light when
No 1 spark plug fires. Connect the leads
according to the instructions supplied with
the light
3Distributor spanner - On some models,
the hold-down bolt for the distributor is
difficult to reach and turn with conventional
spanners or sockets. A special spanner like
this must be used
7.9a Flywheel “OT” timing mark 7.9b Flywheel “OZ” timing mark

Refer to the information on page 0-7 at the
front of this manual before detaching the
cable.
Note: If, after connecting the battery, the
wrong language appears on the instrument
panel display, refer to page 0-7 for the
language resetting procedure.
1Disconnect the battery negative cable.
Bosch alternator
2Remove the voltage regulator from the back
of the alternator (see Section 16).
3Measure the length of the brushes (see
illustration). They should not be less than
6.0 mm. If any are worn past this point, renew
them all as a set. 4Also check for excessively worn slip rings
(see illustration 16.5).
5The brushes are retained either by set
screws or by solder. If you are not skilled at
soldering, it may be best to have an auto
electrician fit the new brushes. Note: Be
careful not to apply heat to the solder joint for
more than 5 seconds. If necessary, use a heat
sink to capture the excess heat. This can be
accomplished by clamping a pair of needle-
nose pliers next to the solder joint.
6On the screw type, hold the assembly in
place and refit the screws. Tighten them
evenly, a little at a time, so the holder isn’t
distorted.
7Refit the regulator assembly to the
alternator.8Reconnect the battery negative cable.
Motorola alternator
9Remove the alternator.
10The brushes are mounted under the
regulator on the rear of the alternator (see
illustration 16.7).
11Remove the mounting screws and
insulating washers, and separate the voltage
regulator and brush holder from the brush end
housing.
12Measure the length of the brushes (see
illustration 17.3). If any brush is less then
6.0 mm long, renew them all as a set.
13Make sure the brushes move smoothly in
the holder.
14Refit the brush holder/regulator. Tighten
the screws securely. Make sure the brushes
aren’t earthed.
15Refitting is the reverse of removal.
18 Starting system- general
information and precautions
The sole function of the starting system is
to turn over the engine quickly enough to
allow it to start.
The starting system consists of the battery,
the starter motor, the starter solenoid, the
ignition switch, and the wires connecting
them. The solenoid is mounted directly on the
starter motor. The starter/solenoid motor
assembly is fitted on the lower part of the
engine, next to the transmission bellhousing.
When the ignition key is turned to the Start
position, the starter solenoid is actuated
through the starter control circuit. The starter
solenoid then connects the battery to the
starter, and moves the starter pinion into
mesh with the flywheel ring gear. The battery
supplies the electrical energy to the starter
motor, which does the actual work of cranking
the engine.
The starter motor on some manual
transmission vehicles can only be operated
when the clutch pedal is depressed. On a
vehicle equipped with automatic
transmission, the starter can only be operated
Engine electrical systems 5•11
17.3 Check the brush length in the normal
rest position (spring uncoiled)
5
16.7 Exploded view of the Motorola alternator