Poor Driveability

Conditions.
No diagnostic trouble codes.

Diagnostic Procedure.
General fault diagnosis rules for poor driveability are difficult to concretize. However, some hints and advice are given in the following.

1. Check the engine coolant temperature.
Cold starting and warm-up trouble may be caused by the engine coolant temperature sensor indicating excessively high engine temperature.

- Connect an ISAT scan tool.
- Contact the Trionic system.
- Select "READ FUNCTIONS".
- Select "COOLANT TEMP".
- Read off the engine coolant temperature.
- Then contact the Integrated Central Electronics (ICE).
- Select "READ VALUES".
- Select "COOLANT TEMP".
- Read off the engine coolant temperature as a reference.

The difference between the two temperature readings may be 50°C (90°F) due to tolerances.

Note if the Trionic system receives no reference ground on pin 66 from crimped connection J68, it will show about 20°C (36°F) too high a coolant temperature even if the temperature sensor is OK.





2. Check pressure sensor operation
Driveability problems may arise if the pressure sensor does not provide the correct voltage across the entire pressure range.

- Check pressure sensor operation.
- Turn the ignition switch to the ON position and then back to the OFF position.
- Select "READ FUNCTIONS".
- Select "INTAKE PRESSURE".

The ISAT scan tool should show a reading of about 102 kPa (NOTE: the reading is dependent on air pressure).

- First build up a positive pressure of 0.6 bar and then create a negative pressure of -0.6 bar. Use a presure gauge and pressure/vacuum pump.

The ISAT scan tool should show readings of 160±5 kPa and 40±5 (it may show somewhat lower readings at high altitude).
If any reading is not OK, change the pressure sensor.





3. Check for leakage

- Check the hose connected to the fuel pressure regulator for leakage.

4. Check the electrode gap

The spark plugs' electrode gap is extremely important for the proper running of the engine.

The spark plug gap should be 1.0+0.1 - 0.0 mm
Too wide a gap will cause misfiring under full load conditions.

Too small a gap will result in lumpy idling and hesitant running under light load conditions.

5. Check the spark plugs' insulator tip

- Check the color of the spark plugs insulator tip.

If the insulator tip of any plug is noticeably lighter in colour it may be because this cylinder receives too weak a mixture.

- If this is the case, check the flow capacity of the injectors.