Page 61
Maintenance Program
110-19
r'-'-',
i
I
L __ --l
®
IKlIlJJJJIIIIIII
Fig. 30. Power steering fluid reservoir.
89136
Replacement of the control arm ball joints is covered in 631
Ball Joints. Replacement of the steering rack tie rod ends is
covered in 643 Tie Rod Ends.
Shock Absorbers and Bushings
Inspect the shock absorber bushings carefully, especially
checking the lower bushing. See Fig. 31. If the lower bushing
is worn, there is usually a constant clunking sound when traveling over rough road surfaces. The shock absorber's function
should also be periodically checked. See 731 Front Suspension for a quick check of the shock absorber condition.
NOTE
Fig. 31. Shock absorber bushings should be inspected (arrows).
Correct tire inflation pressures are important to handling
and stability, fuel economy, and tire wear. Tire pressures
change with temperature. Pressures should be checked often
during seasonal temperature changes. The correct inflation
pressures for cars covered by this manual are listed in the
glovebox owner's manual. Tire pressures are also listed on a
sticker located on one of the door jambs. Notice that the pressures should be higher when the car is more heavily loaded.
All inflation pressures are for cold inflation. That is, when
the car has not been driven for at least three hours, orfor more
than one mile after sitting for at least three hours.
Individual shock absorber bushings are available through an
authorized Saab dealer.
WARNING
Tires
For stability and car control, the wheels and tires must be of
the correct size and in good condition. Tires must be inflated
to the recommended air pressures and the wheels must be in
proper alignment. For maximum safety and best all-around
handling, always install replacement radial tires having the
same specifications. When possible, all four tires should be
replaced at once, or at least in pairs on the front or rear. New
tires do not provide maximum traction, and should be broken
in gently forthe first 100 miles (160 kilometers) or so.
Do not inflate any tire to a higher pressure than the tire's maximum inflation pressure listed on the sidewall. Use care when
adding air to warm tires. Warm tire pressures can increase as
much as 4 psi (0.3 bar) over their cold pressures.
To promote even wear and maximum tire life, Saab recommends rotating the tires from the front to the rear on the same
side at the specified intervals listed earlier. Owing to the car's
suspension design, the front tires begin to wear first at the outer shoulder and the rear tires begin to wear first at the middle
of the tread or inner shoulder.
Tightening torques
NOTE
Be sure to also check the compact spare tire condition and inflation pressure. Keep the spare inflated to 60 psi.
• wheel lug nuts
• wheel lug bolts
90-110 Nm (66-81 ft-Ib)
105-125 Nm (77-92 ft-Ib)
CHASSIS SERVICE
Page 62
110-20
Maintenance Program
Front Wheel Alignment
Air Bag System
Saab recommends checking the 'front and rear wheel alignment at the specified interval or whenever new tires are installed. Only the front wheel alignment is adjustable. See 601
Wheel Alignment for a more detailed discussion of alignment
requirements and specifications.
The air bag should be replaced every 10 years. See an authorized Saab dealer for all service relating to the SRS air bag
system.
WARNING
BODY MAINTENANCE
Maintenance of the body includes lubricating various hinges, locks and slides.
Lubricate the seat runners with multipurpose grease. Do
not apply any oil to rubber parts. Lubricate the sunroof guide
rails with silicone spray. If door weatherstrips are sticking, lubricate them with silicone spray or talcum powder. The hood
release cable should be lubricated as well. The radio antenna
mast should be cleaned and lubricated with a product such as
WD-40.
The door locks, hinges and lock cylinders can be lubricated
with an oil that contains graphite. The body and door hinges,
the hood latch, and the door check rods should be lubricated
with SAE 30 or SAE 40 engine oil. See Fig. 32.
On cars equipped with an SRS airbag system, do not attempt
to service the air bag, the wiring in the steering wheel, the
steering column assembly, or the airbag control unit. The airbag may ignite causing injury. See an authorized Saab dealer
for all service and repairs to the SRS airbag system.
ROAD TEST
As a final check, the car should be taken for a test drive.
Check the overall condition of the various systems, noting especially the function of the brakes, clutch, general engine performance and driving comfort. Check that the cruise control
system and the air conditioning system are functioning correctly. See Fig. 33.
Fig. 33. Road test.
Fig. 32. Exterior body lubrication points.
ROAD TEST
Page 63
Engine-General
200-1
200 Engine-General
General
200-1
Engine Assembly
200-1
Cylinder Head, Camshaft and Valve Train
200-1
Cylinder Block
200-2
Cranksha.ft and Bearings
200-2
Lubrication System. . . . . . . . . . . . . . . . . . . . . 200-2
Fuel Supply and Fuel Injection
200-3
Cooling System. . . . . . . . . . . . . . . . . . . . . . . . 200-3
Turbocharger
200-4
Automatic Performance Control (APC)
200-4
Engine Mechanical Troubleshooting. 200-4
Troubleshooting Basics
200-4
Noise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200-4
Fluid Leaks
200-5
Smoking
200-5
Excessive Oil Consumption
200-5
Poor Fuel Consumption and Low Power
200-5
Engine Not Running
200-5
Driveability Troubleshooting
Warnings and Cautions
Mechanical Condition
Carbon Deposits
Tune-up and Preventive Maintenance
Basic Adjustments
Oxygen Sensor
Air Flow Measurement and Vacuum Leaks
Electrical System
Battery Volta.ge
Wiring and Harness Connectors
Ground Connections
Fuel System
Fuel Supply
200-6
200-7
200-7
200-7
200-8
200-8
:-:-:.:-:.:-:.:.:-:-:-:.:-:
200-8 ;-:-:.:-:-:-:.:-:.:-:-:-:.;
200-9
200-9
!.:(M:::!
200-9
200-10
200-10
200-11
200-11
1'111
TABLES
a. Engine Specifications
b. Engine Mechanical Troubleshooting
c. Engine Management-Driveability
TroubleshoO"ling
200-2
200-6
200-12
GENERAL
inder block. Replaceable valve guides are press-lit into the
cylinder head.
Engine Assembly
The camshafts are driven by a single chain and operate directly on the valves via hydraulic cam followers. The valves
are made of steel and have chromium plated stems. The intake valve heads are induction-hardened and the exhaust
valve heads are coated with stellite.
Two basic engine configurations are used in the 16-valve
cars covered by this manual. On all 1985 through 1990 models and on 1991 and later turbo models, a 2.0 liter engine is
used. On 1991 and later non-turbo models, a 2.1 liter engine
is used. See Table a for complete specifications.
Hydraulic
cam follower
Cylinder Head, Camshaft and Valve Train
The twin-overhead-cam cylinder head assembly is a light
aluminum alloy casting. Bolts hold the cylinder head to the cyl-
87016
Fig. 2. Valve train,
Fig. 1. Cylinder Head,
GENERAL
Page 64
200-2
Engine-General
Table a. Engine Specifications
Model
Year
I
I
900
900S
Convertible
,
I
Displacement
cc (cu. in.)
i
i
i
Compression
ratio
I
Horsepower
@rpm SAE net
i
I
Torque Ib-ft
@rpm SAE net
Fuel System
10.1: 1
125 @5500
128 @3000
Bosch LH 2.2
1985 (121)
10.1: 1
128 @6000
128 @3000
~ Bosch LH 2.4
1989-1990
1985(121)
10.1: 1
128 @6000
128 @3000
I
1991-on
2118 (129)
10.1 :1
140 @6000
140 @2900
I
9.0:1
160 @5500
188 @3000
I
90'1
••
160 @5500
188 @3000
160@5500
188@3000
1986-1987
1985(121)
1988
1985 (121)
1985-1988
900 Turbo
Turbo
Convertible
1989-on
900 Turbo SPG
1985-1986
I
I
I
I
Bosch LH 2.4
Bosch LH 2.4.2
Bosch LH 2.2
!
1985 (121)
1985 (121)
II
i
9.0:1
I
I
1987-1988
1985 (121)
1990-1991
1985 (121)
1985(121)
195 @3000
I
I
1989
165 @5500
9.0:1
~ 175 @5500
9.0:1
I
I
165 @5500
9.0:1
I
I
195 @3000
I
195 @3000
Bosch LH 2.4
Bosch LH 2.2
Bosch LH 2.2
-I
I
- -
Bosch LH 2.4
Bosch LH 2.4
I
I
Cylinder Block
The cylinder block is made of cast iron. The cylinder bores
are drilled straight out of the block and are surrounded by
cooling jackets. The block also contains oilways, or channels,
for the lubrication system.
Fig. 4.
i
i
I
I
L--____________________
Crankshaft and bearings.
on replaceable oil filter and into the engine oil passages. All
models covered by this manual have a low-ail-pressure warning system. Turbo models use an engine oil cooler to help
,mOderate engine oil temperature.
Fig. 3. Cylinder block.
!
Crankshaft and Bearings
The crankshaft is a steel forging. The crankshaft journals
are ground, hardened, and treated with a ''Tenifer'' treatment.
This provides a hard, non-metallic surface to help prevent
bearing seizure. The crankshaft is supported by five main
bearings. End float, or thrust, is controlled at the center bearing. Oilways are drilled into the shaft for bearing lubrication.
I
I
I
I
I
Lubrication System
The lubrication system has forced-flow circulation. The oil
pressure is generated by a separate gear-type oil pump driven directly off the crankshaft. The oil is forced through a spin-
GENERAL DESCRIPTION
i
i
87039
Fig. 5. Lubncation system.
Page 65
Engine-General
Fuel Supply and Fuel Injection
The fuel supply system stores the fuel and provides the fuel
injection system with a constant flow of pressurized, clean fuel.
While there is some variation in components, all Saab 900
models have an electric, in-tank fuel pump and an in-line fuel
filter. The injection-molded plastic fuel tank is located beneath
the car, behind the rear seat. The fuel gauge sending unit and
the electric fuel pump are mounted in the top of the tank.
All Saab 900 16-valve models use a Bosch LH fuel injection
system. LH fuel injection is completely electronicin operation.
Airflow is measured electronically, and a proportional amount
of fuel is metered by electrically opening and closing the fuel
injectors.
In LH fuel injection, many sensors supply information about
engine operating conditions to a central electronic control
unit. The control unit then calculates the amount of fuel needed for the correct air-fuel ratio and opens the fuel injectors,
once for each engine revolution. The amount of fuel metered
200-3
to the engine is determined solely by how long the injectors
are open.
Cooling System
The engine cooling system relies on a closed system of circulating coolant to maintain an even engine temperature and
help transfer heat away. The closed system becomes pressurized at normal engine operating temperature. Under pressure, the boiling point of the coolant is increased, allowing the
engine and cooling system to operate at higher temperatures
without boiling the coolant.
The coolant pump is driven mechanically by the engine using a V-belt. Coolant circulates through the engine to the radiator and heater core, and from the radiator back to the pump.
Before the engine is up to normal operating temperature, the
flow of coolant is controlled by a thermostat. When closed, the
thermostat forces coolant to bypass the radiator and return directly to the coolant pump. This retains as much heat as possible until the engine is warm.
-
5
t
87089
1.
2.
3.
4.
Fuel pump
Fuel filter
Fuel rail
Fuel pressure regulator
Fig. 6.
5.
6.
7.
8.
Fuel retum line
Fuel injectors
Electronic control unit
Ignition coil
9.
10.
11.
12.
Temperature sender
Throttle position switch
Air mass meter
System relay
13. Fuel pump relay
14. Adaptive Idle Control (AIC)
valve
15. Oxygen sensor
LH fuel injection system.
GENERAL DESCRIPTION
Page 66
-200-4
Engine-General
An electric cooling fan, located behind the radiator, is thermostatically controlled so that it runs only when the coolant
has reached a certain temperature. An auxiliary electric cooling fan is located next to the main cooling fan and operates in
addition to the first fan when necessary or when the air conditioning system is on.
Turbocharger
The turbocharger is an exhaust-driven pump that forces air
into the cylinders at higher than atmospheric pressure. This
allows the engine to burn more fuel and therefore produce
more power.
4 .....-<::==
The turbocharger unit consists of two wheels mounted on a
common rotating shaft. One of the wheels, called the turbine,
is driven by the exhaust gas. The other wheel, called the compressor, is located in the intake air stream and compresses
the intake air.
B7087
Fig. 8. The APe system control unit (4) receives Input signals from
three components: the ignition distributor (3), the knock sensor (1), and the pressure sensor (2), The control unit controls
boost pressure via the solenoid valve (5),
ENGINE MECHANICAL
TROUBLESHOOTING
Compressor
wheel
B7086-S5865
Fig. 7. Turbocharger, showing exhaust gas flow (black arrows) and
intake air flow (white arrows),
The turbine is equipped with a waste gate-a pressure controlled valve that automatically bleeds off any excess pressure. If the boost pressure exceeds the predetermined value,
in spite of the waste gate, a pressure switch will temporarily interrupt the fuel supply to the engine.
When the intake air is compressed by the turbocharger, its
temperature rises and its density decreases. To ensure that
the air is as cool and dense as possible to burn the most fuel,
the compressed air is routed through an intercooler before it
enters the combustion chamber. The intercooler can cool the
air by as much as 110°F.
Automatic Performance Control (APC)
The APC system is used on all 16-valve turbo cars. The
APC system continually monitors engine detonation or knock
and adjusts the turbocharger boost pressure accordingly.
ENGINE MECHANICAL TROUBLESHOOTING
This troubleshooting section applies to problems affecting
the basic engine assembly, including the cylinder block, cylinder head, and their internal moving parts. For problems relating to how the engine runs and its overall driveability, see
Driveability Troubleshooting below. For troubleshooting
specific cooling system, ignition system, fuel system, or turbocharger/APC system problems, see the appropriate main repair group under 2 ENGINE.
Troubleshooting Basics
Only a few basic functions are required of the engine. The
block, cylinder head, and their moving parts must fit together
properly, operate smoothly, seal well enough to create and
maintain compression, and keep pistons, valve train, and ignition properly timed. The problems discussed below are those
that affect one or more of these functions.
Noise
In order to run smoothly under harsh conditions, the internal
engine parts are madeto precise dimensions, assembled with
precision clearances, and lubricated by a pressurized oiling
system. Most unidentified engine noises result from clearances that have become too large due to worn parts, lack of adequate lubrication, or both.
Page 67
Engine-General
Rumbling or groaning from the engine compartment may
not indicate engine problems at all, but rather a worn bearing
or bushing in an engine-driven accessory. They include the
coolant pump, the alternator, the power steering pump, and
the air conditioning compressor. To check these, run the engine briefly with the drive belt disconnected and see if the
noise has stopped. Once the drive belt is removed, turning the
pulley and shaft by hand may also reveal a bad bearing or
bushing. A properly functioning accessory should turn
smoothly.
200-5
Excessive Oil Consumption
Some oil consumption is normal. This is why the oil level
must be checked, and occasionally corrected, between oil
changes. Aside from leaks, increased oil consumption will
usually be accompanied by some smoking, however slight.
The causes of excessive oil consumption are the same as
those for oil smoke in the exhaust. As with smoking symptoms, gradual increases are caused by worn piston rings,
valve guides or a failed turbocharger, where applicable. Sudden high oil consumption suggests broken piston rings.
Fluid Leaks
Poor Fuel Consumption and Low Power
Fluid leaking from the engine is most likely either
oil, coolant, brake fluid, or power steering fluid. Look for wet
spots on the engine to help pinpoint the source. It may be
helpful to start by cleaning the suspected area.
The most common areas of engine oil leaks are the timing
chain cover, the engine end plate (flywheel end), the crankshaft oil seals, the cylinder head cover gasket, the transmission-to-engine mating surface, and the oil filter seal.
A pressure test of the cooling system is the best way to discover and pinpoint coolant leaks. Coolant is a mixture of water
and anti-'freeze, yellow-green in color or perhaps brown if the
coolant is old. See 261 Radiator and Cooling System for
more information.
The brake system and power steering system are other
sources of leaks near the engine. Brake fluid is clear, perhaps
slightly purple, and a little slippery. Look for wet spots around
the master cylinder or brake lines. Especially check the flexible
hoses near the wheels. See 5 BRAKES for repair information.
Smoking
Smoke that is visible at the tailpipe is usually either bluegray smoke from burning oil, or white steam from the cooling
system. The color of the smoke identifies the contaminant.
Blue-gray oil smoke in the exhaust usually indicates general engine wear. If smoking is most obvious under high engine
vacuum, such as while coasting at high rpm, valve guide oil
seals or worn valve guides are the most likely cause.
Poor fuel consumption and low power can suggest problems with the fuel, ignition, or turbocharger systems, particularly on a low-mileage engine. On an engine with high
mileage, engine wear and low compression may be the
cause. Normal wear of the valves, piston rings, and cylinder
walls decreases their ability to make a good seal. The engine
becomes less efficient and has to work harder, using more
fuel to produce the same amount of power.
All 16-valve naturally-aspirated engines are equipped with
Bosch ElK ignition. All 16-valve turbo models are equipped
with an Automatic Performance Control (APC) system. These
systems continuously monitor engine detonation to adjust either ignition timing (ElK) or turbocharger boost pressure
(APC) to achieve maximum engine performance.
If either the ElK or APC system detects a faUlt, a set of predetermined values are used to prevent engine damage
caused by detonation. This means the engine is slightly detuned to safely run on all gasoline octane ratings. If low power
is experienced, be sure to check the operation of these systems. The ElK system is covered in 340 Ignition System.
The APC system is covered in 291 Turbocharger.
NOTE
• In order for the ElK and APC system to operate most efficiently, the engine is allowed to knock occasionally. A limited
amount of knock is considered normal.
• The ElK control unit has built-in diagnostic capabilities. A
fault will show up as a series of pulses on the "CHECK ENGINE" light. These pulses will continually repeat themselves
with a brief pause between sequences. For more information
on ElK on-board diagnostics, see 340 Ignition System.
NOTE
• See 291 Turbocharger for additional troubleshooting where
applicable.
• Oil smoke or steam appearing suddenly in the exhaust,
along with low compression pressure in one or more cylinders,
is probably due to a failed cylinder head gasket. Look for bubbles in the coolant or coolant loss, oil in the radiator, or water
in the oil (that tums the oil an opaque, creamy brown).
• Black smoke is caused by the engine getting too much fuel.
See 240 Fuel Injection for more troubleshooting information.
Engine Not Running
An engine problem that affects ignition or valve timing may
prevent the engine from starting or running. The camshaft timing chain and sprockets are responsible for correctly timing
the actions of the valves and the ignition system. A worn timing chain may jump teeth, throwing off all the engine's timing
ENGINE MECHANICAL TROUBLESHOOTING
Page 68
200-6
Engine-General
functions, and still appear to be perfectly normal. To accurately check camshaft timing, see 215 Camshaft Timing Chain.
DRIVEABILITY TROUBLESHOOTING
Table b lists additional symptoms of engine mechanical
problems, their probable causes and suggested corrective actions. The boldface numbers in the corrective action column
indicate the heading in this section of the manual where the
applicable test and repair procedures can be found.
This heading covers general engine management princIples and the basic requirements that allow an engine to run
smoothly. Therefore, effective troubleshooting of specific running conditions can only take place after all of the common
problem areas listed below have been eliminated as a source
of trouble.
Most driveability problems are complex in nature. Therefore, a logical method needs to be used to isolate the trouble
area. Always begin with the simplest and most fundamental
engine management basics. Jumping to conclusions or
Table b. Engine Mechanical Troubleshooting
Symptom
1. Pinging or rattling noise under load, uphill or
accelerating, especially from low speeds.
Indicates detonation or pre-ignition
Probable cause and corrective action
a. Fuel octane level too low, use higher octane fuel
b. Engine running too hot, overheating. Check for cooling system faults. See 261
Radiator and Cooling System
c. Spark plugs damaged or wrong plug type installed. Replace plugs. See
340 Ignition System
d. Air-fuel mixture too lean due to air leaks or low fuel pressure, See 240 Fuel Injection
2. Light metallic tapping noise, varies directly
with engine speed. Oil warning light not
illuminated
a. Low oil pressure, defective warning light circuit. See 220 Lubrication System
3. Light metallic knock, varies directly with
engine speed. Oil warning light blinking or
fully illuminated (may be most noticeable on
hard stops or cornering)
a. Low oil level, correct if necessary
4. Blue-gray exhaust smoke, oil fouled spark
plugs. Indicates oil burning in combustion
chamber
5. White steam in exhaust
b. Faulty hydraulic cam follower. See 214 Cylinder Head and Valve Mechanism
b. Oil flow restricted. Replace oil filter. See 1 LUBRICATION AND MAINTENANCE
c. Low oil pressure. Check oil pressure. See 220 Lubrication System
a. Faulty valve stem oil seals or valve guides. See 211 Cylinder Head Removal and
Installation
b. Worn, broken, or incorrectly installed pistons or piston rings. See 212 Pistons,
Connecting Rods, Cylinder Bores
a. Failed cylinder head gasket or warped cylinder head (probably accompanied by low
compression). Replace or resurface cylinder head and gasket as necessary. See 211
Cylinder Head Removal and Installation
b. Cracked cylinder block. Replace engine or short block. See 212 Pistons,
Connecting Rods, Cylinder Bores
6. Black exhaust smoke
a. Air-fuel mixture too rich due to faulty fuel injection component. See 240 Fuel
Injection
7. Screeching or squealing noise under load.
a. Loose, worn, or damaged V-belt(s). Inspect, replace, or tighten belt(s). See
1 LUBRICATION AND MAINTENANCE
Goes away when coasting. Indicates
slipping V-belt
8. Growling or rumbling, varies with engine
rpm. Bad bearing or bushing in an enginedriven accessory
a. Remove belt from engine driven accessory and check for play, bearing roughness, or
loose mountings
9. Check engine light illuminated or flashing
a. EZK ignition system on-board diagnostics fault detected. Check fault codes. See
340 Ignition System
b. LH fuel injection control on-board diagnostics fault detected. Check fault codes. See
240 Fuel Injection.
10. Engine will not start or run. Starter operates,
engine turns over at normal speed
a. No spark to spark plugs. Check ignition system. See 340 ignition System
b. Incorrect valve timing. Check camshaft timing chain for wear. See 215 Camshaft
Timing Chain
c. No fuel being delivered to engine. See 240 Fuel Injection
ORIVEABILITY TROUBLESHOOTING
Page 69
Engine-General
searching aimlessly for the problem can be time consuming
and frustrating.
NOTE
Models with EZK ignition and models with 2.4 LH and 2.4.2 LH
fuel injection have built-in diagnostic capabilities which will light
the "CHECK ENGINE" light. For more information on EZK diagnostics, see 340 Ignition System. For more information on LH
fuel injection diagnostics, see 240 Fuel Injection.
As with any troubleshooting, careful observation of symptoms is the key to identifying and isolating driveability problems. A test drive can help by demonstrating when the
problem is most pronounced, such as a hesitation that occurs
only when the engine is cold, or a steady miss at high speed.
How has the symptom developed? A symptom that develops quickly is probably caused by a problem that can be corrected by simple maintenance or repair. A symptom that has
developed gradually overtime, especially after sixty or seventy thousand miles is more likely an indication of general wear
and the need for more comprehensive work.
200-7
CAUTION
• Do not connect test instruments with a 12-volt power supply
to terminal 15 (+) of the ignition coil. The current flow will damage the ignition control unit. In general, make test connections
only as specified by Saab, as described in this manual, or as
described by the test instrument's manufacturer.
• Do not disconnect the battery while the engine is running.
• Do not exceed 16 volts at the battery with boosting cables
attached, and do not quick-charge the battery (for boost starting) for longer than one minute. Wait at least one minute before boosting the battery a second time.
• Do not connect terminal 1 (-) of the ignition coil to ground as
a means of preventing the engine from starting.
• Running the engine with a spark plug wire disconnected may
damage the catalytic converter.
• Cleanliness is essential when working with fuel circuit components. Before disconnecting any fuel lines, thoroughly clean
the unions. Use clean tools.
Mechanical Condition
Warnings and Cautions
For general safety, and to protect the sensitive electronic
components, the following warnings and cautions should be
adhered to during any troubleshooting, maintenance, or repair work. Always follow the proper repair and working procedures in the sections that are referenced.
WARNING
• The ignition systems used on the cars covered by this manual are high-energy systems operating in a dangerous voltage
range. Exposure to terminals orlive parts could prove to be fatal. Use extreme caution when working on a car with the ignition on or the engine running.
• Do not touch or disconnect any of the high tension cables
from the coil, distributor, or spark plugs while the engine is running or being cranked by the starter.
• Connect and disconnect ignition system wires, multiple connectors, and ignition test equipment leads only while the ignition is switched off.
• Before operating the starter without starting the engine, disable the ignition. See 340 Ignition System. Do not disconnect
terminal 4 (center terminal) from the coil or remove the distributor cap as a means of disabling the ignition.
• During any test where fuel is discharged, do not smoke or
work near heaters or other fire hazards. Have a fire extinguisher handy.
Before troubleshooting a poorly running engine or an engine that will not start, determine the general condition of the
engine, especially if it has high mileage. If the engine is severely worn or has mechanical problems, the only remedy is
overhaul or repair. If a tune-up or scheduled maintenance is
due, it should be done before proceeding further with troubleshooting.
Only a few basic functions are required of the engine. The
parts must fit together properly, operate smoothly, and seal
well enough to create and maintain compression, and keep
pistons, valve train, and ignition properly timed. General engine condition can be easily assessed by performing a compression test.
NOTE
Saab does not give specific compression pressure specifications. In addition, a compression test requires special equipment. If the equipment is not available, most automotive repair
shops can do these tests quickly and at a reasonable cost.
Carbon Deposits
Carbon deposits on the fuel injectors and the intake valves
will affect the way the engine idles and runs. See Fig. 9. Even
a ten percent decrease in the amount of fuel that the injectors
deliver will cause driveability problems. These deposits normally form during the "hot soak" period immediately after the
engine is turned off, at which point the engine temperature rises slightly for a short period.
ORIVEABILITY TROUBLESHOOTING
Page 70
200-8
Engine-General
Replacement schedules and procedures for the spark
plugs, spark plug wires, distributor cap, ignition rotor, fuel filter, air filter, oxygen sensor, and oil and oil filter are given in
1 LUBRICATION AND MAINTENANCE.
NOTE
For information on inspecting ignition components, see 340
Ignition System. For information on checking the oxygen
sensor, see 254 Exhaust Emission Control.
Basic Adjustments
Fig. 9.
Examples of carbon deposits on fuel injector (left) and intake
valve (right). Carbon deposits can cause a rough idle, hard
cold starting, and overall poor performance.
Driving style may be the main contributor to the problem. A
car that is predominantly driven on short trips around town or in
city traffic seems to increase the likelihood of deposits forming.
Carbon deposits on the intake valves and injectors should
be removed prior to troubleshooting driveability problems.
Special fuel injector test equipment is required to accurately
check for clogged injectors. If the injectors are severely
clogged, they can be removed and visually inspected. Inspecting the intake valves is more difficult because the intake
manifold must be removed. Check with an authorized Saab
dealer for the latest information on carbon deposits and the
best methods to remove them.
CAU'nON
Always follow the manufacturer's directions when using fuel
additives designed to remove carbon deposits and clean injectors. As a general rule, high detergency fuels should not be
used together with fuel additives. The additional cleaner in the
fuel can dilute engine oil and accelerate engine wear.
In addition to tune-up component replacement, it is important that all of the basic adjustments that can be made are correctly set. Check idle speed, idle mixture (%CO), and ignition
timing to be sure they are all within the specified limits. See
1 LUBRICATION AND MAINTENANCE.
NOTE
All of the basic adjustments require the use of specialized test
equipment. If any of the test equipment is not available, it is
recommended that the adjustments be done by an authorized
Saab dealeror other qualified repair shop. These adjustments
can be made quickly and at a reasonable cost.
The systems that adapt the idle mixture (Lambda system),
idle speed (AIC system), ignition timing (EZK system, where
applicable), and turbo boost pressure (APC system) can only
correct engine operation within a limited range. Once these
limits are exceeded, driveability problems will become noticeable. For example, the oxygen (Lambda) sensor can adapt
idle mixture for things such as a small vacuum leak or minor
engine wear. A large vacuum leak or a severely worn engine
may exceed the operating range of the sensor, causing the
engine to run lean. If large adjustments are necessary, the
faults that are causing these incorrect settings should be corrected prior to making any adjustments.
Oxygen Sensor
Tune-up and Preventive Maintenance
A tune-up is regular maintenance of the ignition and fuel
system components for normal wear and contamination. The
condition of the tune-up and emission control components
can affect engine performance and drive ability. The ignition
components all carry high voltage to deliver a precisely timed
spark to ignite the air-fuel mixture. If any of these components
are faulty or worn, the intensity and timing of the spark will be
affected. Dirt contamination of fuel system and emission control components can adversely affect fuel delivery, air-fuel
mixture, and exhaust emissions.
When experiencing driveability problems, a good starting
point is to do a tune-up. Many driveability problems are eliminated by simply replacing these components.
ORIVEABILITY TROUBLESHOOTING
The oxygen sensor, also called the Lambda sensor, affects
the air-fuel mixture by sending a varying voltage signal to the
fuel injection control unit. The sensor is positioned in the exhaust stream and actually measures the amount of oxygen in
the exhaust gas so that the fuel injection system can correctly
adjust the air-fuel mixture. See Fig. 10. A high concentration
of oxygen in the exhaust gas indicates a lean mixture and a
low content indicates a rich mixture.
NOTE
The control unit ignores the signal from the oxygen sensor until the engine reaches a specified temperature. Therefore,
when troubleshooting cold engine driveability problems, the
oxygen sensor can be ruled out as a possible cause.