Why Does a Diesel Engine Shake at Idle When Cold?

[DeKaylee]

Diesel engine shaking at idle when cold occurs because the temperature inside the engine is insufficient, and both the fuel and lubricating oil are not warm enough. Therefore, during a cold start, more fuel should be injected to meet the power requirements. The larger the spark plug gap, the smaller the ignition energy. At low temperatures, fuel atomization is poor, requiring higher ignition energy. Over prolonged use, the spark plug's ignition gap tends to widen, leading to reduced ignition energy, which affects performance and causes the vehicle to shake. Diesel engines and gasoline engines share fundamentally similar structures, including the cylinder block, cylinder head, piston, valves, connecting rod, crankshaft, camshaft, and flywheel. However, the former operates by compressing and igniting diesel, while the latter ignites gasoline—compression ignition versus spark ignition being the fundamental difference between the two.