Why Does the Volvo S90 Engine Shake When Cold?

[DeEzra]

Volvo S90 engine shaking when cold can be attributed to the following reasons: 1. Low ignition energy at low engine temperatures. When the engine temperature is insufficient, both fuel and lubricant temperatures are low, requiring more fuel injection during cold starts to meet power demands. Larger spark plug gaps result in weaker ignition energy. Poor fuel atomization at low temperatures demands higher ignition energy. Over time, spark plug gaps tend to widen, reducing ignition energy and affecting engine performance, leading to shaking. Additionally, aging ignition coils, high-voltage wires, or electrical leaks can also decrease ignition energy. 2. Incorrect engine air-fuel mixture ratio. Improper fuel-air mixture occurs in both open-loop and closed-loop control systems. In closed-loop systems, oxygen sensors require a minimum operating temperature of 370°C. If the exhaust pipe temperature doesn't reach this level upon startup, the oxygen sensor remains inactive. This causes the ECU to miscalculate, leading to errors in fuel-air mixture and ignition timing control, reducing power output and causing shaking. 3. Carbon buildup on engine valves and intake ports. Carbon deposits can absorb fuel (similar to soil absorbing water from a riverbank), causing ECU miscalculations. For instance, if the ECU injects 100 units of fuel-air mixture but only 90 units reach the cylinder (with 10 absorbed by carbon deposits), even complete combustion of the remaining 90 units won't provide sufficient power, inevitably resulting in shaking. 4. Varying cylinder conditions. After prolonged use, clearance between cylinder liners and pistons becomes uneven—some larger, some smaller. During cold starts without proper oil lubrication, cylinders with larger clearances may leak high-temperature gases, reducing power output.

[DiJaxon]

My own Volvo S90 also experienced severe shaking during cold starts, likely due to aging spark plugs or ignition coil issues. At low temperatures when the engine is cold, the oil passages aren't as smooth, leading to uneven combustion and increased shaking. Additionally, carbon buildup on fuel injectors or intake valves can obstruct fuel flow and worsen the vibration. Don't underestimate oil quality - using oil with incorrect viscosity can thicken in cold weather, causing insufficient lubrication and extra vibration. I recommend checking if spark plugs need replacement and regularly using fuel additives to clean carbon deposits, as proper maintenance can prevent major issues. If shaking is accompanied by noise, it might indicate loose engine mounts - get it repaired at a professional shop immediately to avoid long-term engine damage.

[StHaven]

I've thought about this situation for a while. Common causes of cold engine shaking include clogged or imbalanced fuel injection systems. At startup, low temperatures can lead to insufficient fuel supply from the pump or dirty injectors causing abnormal air-fuel mixture concentration, resulting in rough combustion and shaking. Additionally, unstable signals from sensors like the throttle position sensor can also contribute. Start with a simple self-check using an OBD tool to read fault codes - if you see P0300, it indicates misfiring. Also check if the engine oil needs to be replaced with a winter-specific grade. If problems persist, seek professional repair to prevent more expensive damage. Key prevention is allowing the engine to stabilize before shutting off after driving to reduce carbon buildup.

[Leilani]

This shaking issue often stems from the engine's poor adaptation in low temperatures. During cold starts, the engine control unit hasn't warmed up properly, causing an imbalance in fuel mixture regulation that leads to combustion fluctuations and vehicle vibration. For the Volvo S90, an ECU software upgrade may be required to optimize performance. Carbon buildup or intake manifold leaks are also potential causes that require regular cleaning. Using high-quality gasoline and adhering to the manual's recommended engine oil maintenance can alleviate the problem and ensure smooth driving.

[JayceAnn]

To reduce cold engine shaking, start with routine maintenance. Wait a few seconds before starting to allow oil circulation, and use low-temperature fluidity oil to avoid excessive viscosity. Regularly replace air filters and fuel filters to prevent carbon buildup and clogging of the fuel injection system. If issues arise, check the spark plugs and replace them if fouled. Prevention is key to extending engine life and avoiding costly overhauls.