What are the causes of cold start vibration in Audi Q5?
2 Answers
Audi Q5 cold start vibration reasons are as follows: 1. Incorrect air-fuel ratio: The mixture of fuel and air is not properly adjusted, which occurs in both open-loop and closed-loop control systems. In vehicles with closed-loop control, the oxygen sensor's minimum operating temperature is 370 degrees Celsius. 2. Carbon deposits on valves and intake passages: If carbon deposits form on the valves and intake passages of the engine, the ECU may make incorrect judgments because the carbon deposits can absorb a certain amount of fuel. 3. Different cylinder conditions: After prolonged use of the engine, the gaps between each cylinder liner and piston will vary in size, meaning some gaps are larger and others smaller. During a cold start, without proper lubrication from the engine oil, cylinders with larger gaps are prone to leaking a certain amount of high-temperature gas, thereby reducing power output.
Having driven for decades, the most common causes of Audi Q5 shaking during cold starts are: first, excessive carbon buildup clogging the intake tract or intake valves, leading to unstable combustion due to incorrect air-fuel mixture concentration; second, aging spark plugs causing insufficient ignition energy and unbalanced cylinder operation; third, low fuel pump pressure or dirty fuel injectors resulting in uneven fuel delivery affecting startup; fourth, loose engine mounts failing to absorb vibrations, with rubber deterioration common in older vehicles; fifth, issues with the air-fuel ratio sensor providing inaccurate signals that disrupt ECU control. For regular maintenance, periodic throttle body cleaning and timely spark plug replacement are recommended as preventive measures.
