What causes the Audi A4L to shake and stall during cold starts?

[LincolnDella]

Audi A4L shaking and stalling during cold starts may be due to dirty fuel lines, low engine temperature, and other reasons. Dirty fuel lines: When the fuel lines are dirty, the fuel injectors' atomization efficiency decreases, leading to poor combustion. The sensors detect this issue, causing severe shaking and stalling, which is occasional. Cleaning the system will resolve the problem. During the second ignition, because the engine control unit has data from the first attempt, it increases the fuel injection volume to ensure sufficient air-fuel mixture, preventing stalling. Low engine temperature: During a cold start, the engine temperature has not yet reached its optimal operating level. At this time, the fuel injectors automatically increase the fuel injection volume to raise the RPM, with idle speed ranging between 1,200 and 2,000. After idling for about a minute, the RPM drops below 1,000, and the engine returns to normal operation.