Visual inspection (Audi 100 C4)

First, check the air ducts for leaks! All hoses from the thick air intake hose to the thin vacuum hoses should be checked.

Are the injection nozzle seals and intake flange gaskets in good condition?

Leaky areas allow access to unaccounted air, i.e. air that is not accounted for by the system and therefore significantly interferes with the preparation of the mixture. The mixture is uncontrollably depleted. The consequence of this is engine malfunctions, manifested primarily in uneven idling.

Warm up the engine to operating temperature, then let it idle, open the hood, and disconnect the plug connection to the lambda probe.

Spray with a spray bottle containing starting fuel (eg, "Startpilot"), intake manifold sealing flange gaskets and other suspicious parts.

If the rotation speed changes when spraying a certain place, it means that there is a leak there.

Is it possible to recognize leaks in fuel line hoses?

Have the wire ends been disconnected and reconnected many times? Corrosion or poor handling may result in poor contact.

Carefully examine the plugs of the individual components of the injection system. They can only be treated with contact spray, but under no circumstances be bent, which can cause malfunctions.

Text provided by the online resource: AudiManual