Poor Driveability

FAULT DIAGNOSIS, POOR DRIVEABILITY

General fault diagnosis procedures for poor driveablity are difficult to recommend.
However, here follow some useful hints and advice.

1. Cold-starting and warming-up problems can be caused by the coolant temperature sensor indicating an engine temperature that is too high.
Connect a Scan Tool.
Select "READ FUNCTIONS".
Select "COOLANT TEMP".
Read the coolant temperature. Then contact the Electronic Display Unit's (EDU) coolant temperature as a reference.
Owing to manufacturing tolerances, the difference between these two temperature readings may be ±5°C.

2. If the mass air flow sensor does not produce the correct voltage across the entire flow rate band, this could give rise to poor driveablity. Check the operation of the mass air flow sensor according to "Control Module Connection Test Readings", pin 7. Pinout Values and Diagnostic Parameters

3. Use a Scan Tool to check that the oxygen sensors of both cylinder banks show the correct voltage change.

If this is not the case it may be due to air leakage in the induction system.
Such air leakage will result in erratic idling, especially after starting from cold, and hesitance when driving with an extremely light load.





4. The spark plug insulators can easily be cracked if the correct tool is not used in the correct manner.
This will generally be noticeable as misfiring when the engine is under load and occurs after a few thousand kilometers of driving.
A defective spark plug is hard to identify as the fracture occurs under the plug body. Further more, the plug works perfectly when tested under pressureless conditions.

5. Check the color of the plug's insulator tip.

If any spark plug has a noticeably lighter color than the others, this could be due to an overlean fuel-air mixture in its cylinder.
If this is the case, carry out flow measurement on the injectors.