Powertrain Management: Adjustments

Service repair no - 19.22.13
The position of the Idle Air Control (IAC) valve can be checked using TestBook and adjusted if necessary through the by-pass screw in the plenum chamber. The bypass screw is covered by a tamper proof plug which can be extracted using a self tapping screw.

Vehicles in certain markets are not fitted with oxygen sensors or active catalytic converters. Certain specification vehicles may have active catalytic converters fitted, but do not use oxygen sensors. This is referred to as an open loop catalyst system. All vehicles without oxygen sensors must have the exhaust CO content checked periodically using an approved CO meter and adjusted if necessary using TestBook.

On vehicles with open loop catalyst systems, exhaust CO content must be checked upstream of the catalyst, NOT at the tailpipe.

Preliminary Checks
1. Ensure that air filter and fuel filter elements are in a serviceable condition.
2. Check air intake system, including vacuum pipes and hoses for correct routing and freedom from leaks and restriction.
3. Electrical connections must be secure and leads correctly routed.
4. Check ignition system integrity using an approved Engine Analyser.

Procedure

Vehicles without oxygen sensors:
5. Ensure exhaust gas analyser is warmed and calibrated ready for use.
6. Non catalyst vehicles: Connect exhaust gas analyser to tailpipe.
7. Disconnect purge valve pipe at charcoal canister.


CAUTION: Do not disconnect purge valve electrical multiplug.







Open loop catalyst vehicles:
8. Remove blanking plug from RH exhaust front pipe, forward of the catalyst.
9. Fit sampling pipe and tighten securely.


CAUTION: Air leaks at the sampling pipe will cause incorrect readings.


10. Connect exhaust gas analyser to sampling pipe.


NOTE: When refitting the blanking plug apply nickel based grease to the thread.







All vehicles:
11. Ensure air conditioning and all electrical loads are off. Vehicle must be in neutral or park with air suspension in kneel and disabled.
12. Carry out tuning or base idle setting procedure as applicable using TestBook.