Poor Performance

Conditions.
No diagnostics trouble codes.





Diagnostic Procedure.
General fault diagnosis procedure for poor performance is difficult to concretize. However, some advice which may be helpful is given in the following.
1. 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 pressure gauge and pressure/vacuum pump.
The ISAT scan tool should show readings of 160 ± 5 kPa and 40 ± 5 kPa respectively (the ISAT scan tool readings may be somewhat lower at high altitudes).

Are the ISAT scan tool readings correct?
YES:
^ The pressure sensor is OK.
NO:
^ Change the pressure sensor.

NOTE: Boost pressure on cars with a manual gearbox is limited in 1st gear.





2. Check the fuel delivery flow
Inadequate fuel delivery flow from the fuel pump or through the injectors may be noticeable when driving the car at wide open throttle.
- Connect an ISAT scan tool.
- Select "READ FUNCTIONS".
- Select "O2S 1".
When the car is driven at wide open throttle the ISAT scan tool should show a reading of > 0.5 V.

Is the ISAT scan tool reading correct?
YES:
^ The fault is probably in the fuel system.
NO
^ See "Fault diagnosis/Components, fuel pump relay/fuel pump.

3. Check for knocking
- Select "READ ON/OFF".
- Select "KNOCK CONTROL".
- Accelerate at wide open throttle from low engine rpm.

Does the ISAT scan tool show "ON"?
YES:
^ Continue with point 4.
NO:
^ Knocking, is not the cause of poor performance.





4. Check the ignition discharge module
- Fit a substitute ignition discharge module
- Repeat the activities described in point 3.

Does the ISAT scan tool sill show "ON"?
YES:
^ The fault is probably due to an inferior grade of fuel. Refit the original ignition discharge module.
NO:
^ The remedial measure taken was correct.