Engine/Exhaust System - Cold Start Idle Characteristics
01 Idle speed characteristic during cold start
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February 14, 2013.
Supersedes Technical Service Bulletin Group 01 number 12-57 dated October29, 2012 for reasons listed below.
360
Vehicle Information
Condition
Technical Background
To comply with the legal requirements on exhaust gas emissions according to the LEV-1 and LEV-2 standards, a high exhaust gas quality must be
ensured. The necessary catalyst only operates at a temperature over 300锟斤拷C (572锟斤拷F). To achieve this, the catalyst is heated up. The catalyst heating
phase is achieved by a late ignition angles and by introducing additional fresh air to the exhaust valves (secondary air system).
Late ignition angles make sure that the exhaust gas from the cylinders has a higher temperature. This exhaust gas includes fuel that is un-burnt, and
was deliberately injected into great quantities. The secondary air system adds fresh air to the exhaust gas as it leaves the cylinder and the extra fuel is
burnt. As a result, the temperatures of the exhaust gas and of the catalyst increase quickly.
Effects:
The afterburning in the exhaust manifold before the catalyst changes the sound characteristic of the engine. This heating-up of the catalyst, including
afterburning, is normal and has no effect on the service life of the engine. During this catalyst heating phase, the engine has increased idle speed,
may have increased vibrations, and has a different sound characteristic.
Conditions for the catalyst heating phase:
Depending on conditions, the time of the catalyst heating phase varies.
Production Solution
361
No change
Service
Please do not repair. Explain the technical background to the customer.
Warranty
This TSB is informational only and not applicable to any Audi warranty.
Additional Information
All parts and service references provided in this TSB are subject to change and/or removal. Always check with your Parts Department and service
manuals for the latest information.
