Tests W/ Codes 2.5L V6: Overview Saab 900 II

Scheme 39

For model year 1994 and later cars, a partially new terminology for all emission-related components, signals and functions has been introduced. This new terminology conforms to a standard agreed upon by the automotive industry and government authorities acting within an organization called the Society of Automotive Engineers (SAE), which has issued a Recommended Practice called SAE J1930.

Local authorities in California (CARB, the California Air Resources Board) require the terms in this J1930 standard to be used in all service literature concerning emission-related systems for model year 1993 and later cars.

For the United States as a whole, the U.S. Environmental Protection Agency (E.P.A.) has proposed that SAE J1930 terminology be required for model year 1994 and later cars.

During a transitional period, the use of this terminology will naturally give rise to a number of problems for all mechanics who have long been accustomed to using the existing terms for Saab components.

However, the intention is that standardization in this field will in the long term reduce confusion and the risk of misinterpretation.

To give an example, what Saab has called an AIC valve is called an "Electronic Air Control Valve Solenoid", "Auxiliary Air Control Valve", "Idle Stabilizer Valve" or "Air Control Valve" by other manufacturers.

On model 1994 and later cars we call it an IAC (Idle Air Control) valve, in accordance with J1930 terminology, which is also what it will be called by the world's other motor manufacturers.

SAE J1930 terminology has not been arrived at on the basis of the terms used by the majority of motor manufacturers. Instead it has been built up by applying certain rules of logic, according to which one or more attributes are added to a basic term in order to define it more precisely.

Let us once again take " Idle Air Control Valve " as an example

1. The basic term is Valve .
2. Control denotes that the valve has a controlling function.
3. Air tells us what the valve controls (air).
4. Idle, finally, describes the kind of air the valve controls - idle air.

To facilitate the transition to this new terminology, a table of Saab's previous terms and their corresponding J1930 designations is given below. Some of the terms included in the table might not be used in this particular Service Manual, but you will no doubt meet them sooner or later in other connections.

Since SAE J1930 terminology is a local market requirement, the changes in terminology will naturally affect other markets to a lesser degree. In spite of this, we believe it is important for you to know about these changes wherever in the world you happen to work. Even if you have no other use for it, you can consult the following table if and when you come across an unfamiliar term.

The table has been compiled to show the difference between the terms previously used and the new J1930 terminology.

The correction abbreviation is given in brackets ().

SAE J1930 TERM REFERENCE CHART

Scheme 40

MOTRONIC 2.8.1 - system description

The Bosch MOTRONIC engine management system controls ignition and fuel injection, as well as air intake when idling, by means of a single control module.

On model year 1994 and later Saab 900 cars with a normally aspirated engine, the MOTRONIC system will be fitted as follows

1. MOTRONIC 2.10.2 for the B206i engine
2. MOTRONIC 2.10.2 for the B234i engine
3. MOTRONIC 2.8.1 for the B258i engine

Both MOTRONIC versions have sequential injection and individual control of the ignition timing when knocking occurs in any of the cylinders (these functions are adaptive).

Expressed in simple terms, it could be said that the MOTRONIC system is a combination of a conventional electronic fuel injection system and an electronic ignition system with a knock sensor. The injection system features sequential injection while the power output stage of the ignition system is integrated in the control module.

With the introduction of the Bosch MOTRONIC system, the earlier LH, CU14 and EZK systems will be discontinued.

Scheme 41

The MOTRONIC 2.8.1 consists of the following main components

1. Control module
2. Ignition coil module with three ignition coils
3. Mass air flow sensor
4. Crankshaft position sensor
5. Camshaft position sensor
6. Knock sensors (2)
7. Throttle position sensor
8. Oxygen sensors (2)
9. Injectors
10. Secondary air injection device
11. Coolant temperature sensor
12. Intake air temperature sensor

Scheme 42

High voltage for the ignition spark is generated in the module containing three ignition coils. Each ignition coil supplies two spark plugs simultaneously with high tension to produce a good spark. Ignition coil 1 thus causes a spark to be produced simultaneously in cylinders 2 and 5, ignition coil 2 in cylinders 3 and 6, and ignition coil 3 in cylinders 1 and 4

The control module and a reference signal from the crankshaft position sensor ensure that correct timing information is supplied to the right ignition coil. As will be realized, the system has no conventional distributor.

The firing order is 1 -2-3-4-5-6.

Depending on engine temperature, idling speed varies between 680 and 800 rpm.

At idling speed the ignition timing normally varies between about 8° and 12°, depending on engine speed and temperature.

In conjunction with upshifts or downshifts on cars with automatic transmission, engine torque is limited by retarding the ignition to -10°, provided that it is already less than this.

Ignition timing is determined by the control module, mainly on the basis of the following information

1. Engine speed (Td)
2. Engine load (Tq)
3. Knocking (if occurring)

IGNITION COIL CYLINDERS REFERENCE CHART

Scheme 43

The V6 engine has two knock sensors, one for the front row of cylinders (2, 4 and 6) and one for the rear row of cylinders (1, 3 and 5).

If knocking occurs in any of the cylinders, the relevant knock sensor sends a signal to the control module.

The control module notes the cylinder in which knocking occurs and retards the ignition in that cylinder by 3° (at engine speeds up to 1200 rpm the ignition is retarded by 2.25°).

If the knocking stops as a result of retarding the ignition, the timing will be restored in steps of 0.75° to what it was before.

On the other hand, if knocking persists in the same cylinder despite its ignition point being retarded by 3°, the control module will retard it an additionally step, and so on. However, the control module cannot retard the ignition by more than 13.5°. At high intake air temperatures (above 50°C), the ignition is also retarded to counteract knocking. When the temperature drops, the ignition is restored to normal in steps of .75°.

When the throttle opens past a certain angle, the control module interprets it as full load and the ignition timing is obtained from another map (Kenn-feld) with lower timing angles.

Should a break in continuity occur in any of the knock sensors or in any of the sensor circuits, the ignition will be retarded by up to 12° in both rows of cylinders (not at idling speed).

Scheme 44

Fuel injection with the MOTRONIC 2.8.1 system is sequential, i.e. it follows the firing order of the engine.

Injection duration is determined by the control module on the basis of a number of parameters

1. engine load (mass air flow sensor)
2. engine rpm (crankshaft sensor)
3. engine temperature
4. oxygen sensors
5. etc.

The V6 engine has two oxygen sensors, one for the front row of cylinders (2, 4 and 6) and one for the rear row of cylinders (1, 3 and 5). With the information from both oxygen sensors, the control module can regulate the injection duration separately for each individual cylinder.

The opening duration of the injectors varies from about 3 ms at idling speed to about 15 ms at full throttle.

Scheme 45

As soon as the engine starts to rotate and the control module receives signals from the crankshaft position sensor, the fuel pump relay operates so that all valves open simultaneously and remain open for a length of time which is dependent on temperature. This takes place only once, i.e. during the first injection, and it is done to achieve shorter starting times. After this initial injection of fuel the system changes to sequential injection.

Scheme 46

Idling speed is controlled by signals sent from the control module to a single-winding IAC valve.

The automatic idling control function is adaptive, i.e. it adapts continuously to the changes taking place throughout the life of the engine. Such changes might be wear in the engine, dirt or leakage in the intake manifold or throttle body, etc.

The control module is programmed to maintain idling speed if the speed of the car 0 km/h at the same time as the throttle position sensor indicates that the butterfly is in the idling position.

To maintain a constant engine speed, air mass compensation takes place on engagement of the A/C or secondary air injection pump and when Drive is selected on cars with automatic transmission.

With a hot engine, idling speed for the MOTRONIC 2.8.1 system is 800 rpm.

Scheme 47

To get the catalytic converter working as soon as possible after a cold start, ambient air is pumped into the two exhaust manifolds where the oxygen in the air starts a chemical combustion process together with CO and HC pollutants, thus generating heat.

About five seconds after the engine fires, the secondary air injection pump starts and a solenoid valve opens the passage leading to the exhaust manifolds.

Since this process is dependent on both time and temperature, the solenoid valve closes and the pump stops either when a maximum of 80 seconds has elapsed or when engine temperature reaches 65°C, whichever occurs first.

At an engine temperature of 20°C (68°F) the pump runs for about 80 seconds.

The pump will start only if the temperature of both the intake air and the coolant is between +1°C and +35°C (33°F - 95°F).

Scheme 48