What Causes the Volkswagen Bora to Shake When Cold?

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Possible reasons for engine shaking upon startup include carbon buildup on valves and intake ports, low ignition energy, and improper air-fuel mixture. Low ignition energy: When the engine is cold, the internal temperature is insufficient, and both fuel and lubricant temperatures are low. More fuel injection is required to meet power demands. Poor fuel atomization at low temperatures requires stronger ignition energy. Causes of low ignition energy may include excessive spark plug gap or faults in ignition coils or high-voltage wires. Improper air-fuel mixture: Inaccurate air-fuel ratio adjustment, oxygen sensor failure, or ECU miscalculations can lead to errors in controlling fuel mixture and ignition timing through actuators. This reduces vehicle power output and results in shaking. Carbon buildup on valves and intake ports: Carbon deposits can absorb a certain amount of fuel, causing the ECU to make incorrect judgments. This also fails to achieve the required power, resulting in shaking.