Why does the Polo shake when starting cold?
2 Answers
Here are the reasons for engine shaking during cold starts: 1. Engine mechanical failure: such as uneven cylinder pressure in each cylinder. 2. Intake system failure: such as excessive dirt inside the intake pipe, etc. 3. Engine management system failure: such as incorrect coolant temperature or intake temperature signals, wiring faults, etc. 4. Ignition system faults: such as excessive carbon buildup on spark plugs or incorrect gap, leakage in high-voltage wires or distributor cap, damaged ignition coil, etc. 5. Fuel supply system failure: such as injectors not sealing properly or clogging due to excessive carbon deposits inside the nozzle. 6. If the engine shaking disappears as the engine temperature rises, it may be caused by excessive carbon buildup on the spark plugs, which burns off as the intake volume increases and temperature rises. Other factors causing engine shaking during cold starts include: 1. Dirty throttle or air flow meter, reducing intake volume, or poor EGR (exhaust gas recirculation) valve performance, introducing exhaust gas at idle. 2. The idle motor controls the bypass intake passage to regulate intake volume; if the voltage is low, operation may be insufficient. Poor fuel quality failing to meet the required heat value, resulting in lower combustion power output.
My old Polo has the same issue. When starting the engine cold, it shakes so much it feels like the car is dancing, especially in winter. I think it might be related to the spark plugs—after prolonged use, they age and cause unstable ignition. Or it could be too much carbon buildup in the throttle body, blocking the air intake. Dirty fuel injectors spraying unevenly can also cause shaking. Last time, I took it straight to the repair shop, and after the mechanic cleaned the throttle body and replaced the spark plugs, it improved a lot. Remember not to delay repairs—ignoring it could damage the engine block or increase fuel consumption. Develop good habits: change the air filter every 20,000 km and replace the engine oil on time to prevent carbon buildup. When starting a cold engine, don’t rush to step on the gas—wait for the RPM to stabilize before driving to reduce the risk of shaking.
