What are the reasons for high engine speed and abnormal noise during cold start?

[StMila]

Cold start with high engine speed and abnormal noise is caused by: dirty engine oil, excessive viscosity, and piston knocking. The reasons for high engine speed are: 1. Sudden increase in throttle opening; 2. Fuel injector dripping or clogging; 3. Slipping or damaged air conditioning clutch; 4. Air intake system leakage; 5. Insufficient engine output power. The solutions for high engine speed are: 1. Adjust the throttle opening; 2. Replace the fuel injector, air conditioning clutch, air intake system, and engine. The function of the engine is: to convert the thermal energy of gasoline into mechanical energy by burning and expanding gas in a sealed cylinder, thereby pushing the piston to perform work.

[AlexAnn]

As an average car owner who frequently drives in cold weather, I've noticed that high engine RPM accompanied by rattling or gurgling noises during cold starts is actually quite common. Often, it's due to oil-related issues. The cold weather makes the oil too thick, so when starting the car, it's like a person stretching after waking up—the engine spins rapidly but with noticeable hesitation, causing friction between components and generating noise. Additionally, old or degraded oil, or using low-quality oil with incorrect viscosity, can exacerbate the problem. Poor fuel injection, such as from dirty injectors spraying inaccurately during cold starts, can also lead to RPM surges and harsh sounds. Sometimes, this is related to clogged air filters or minor internal engine wear, like insufficient lubrication of valve stems. I must emphasize that ignoring these noises could lead to engine damage, such as scoring the cylinder walls, which would be a costly repair. If this occurs, I recommend first changing the oil and cleaning the fuel system. Warming up the car for a few minutes can also help reduce these issues. Of course, if the problem persists, it's best to have a trusted mechanic inspect specific components.

[FinnRose]

From my decade-plus experience as a seasoned driver, when an engine revs high and makes strange noises during cold starts, it's mostly due to fuel supply issues or poor oil circulation. Imagine the car sitting overnight, freezing cold like a block of ice. When you start it in the morning and the RPM spikes, accompanied by metallic grinding sounds or hiccup-like noises, it's likely caused by carbon buildup in the fuel injectors disrupting proper fuel spray and causing erratic RPM. Oil viscosity is also crucial—too thick in cold weather can hinder lubrication, leading to dry friction between shafts and bearings, creating noise. Additionally, worn parts like a loose timing chain can produce clicking sounds, and air leaks in the intake system can cause high idle with a hissing noise. Ignoring these issues long-term can damage engine life, such as causing oil burning. Based on my routine fixes, simply switching to season-appropriate oil and replacing the air filter can help control the problem. If the noises persist, it's best not to push the car and instead get it diagnosed at a repair shop to avoid more serious repairs.

[DiAlejandro]

From a mechanical perspective, a fast-spinning and noisy engine during cold starts often indicates issues with the fuel supply or lubrication system. For example, in cold weather, uneven fuel injection or clogged fuel injectors can cause an imbalanced air-fuel mixture, leading to increased RPM and knocking or squeaking sounds. If the engine oil is too viscous or old, its flow slows down at low temperatures, resulting in insufficient lubrication and potential friction-induced rattling noises. Other factors include intake manifold leaks causing abnormal airflow, malfunctioning sensors leading to inaccurate RPM control, or internal engine components like valve stems lacking lubrication and producing high-frequency noises due to wear. Ignoring these abnormal sounds risks engine overload and damage, making prompt inspection crucial. In practice, start by checking the oil condition and cleaning the fuel system to see if the issue improves; otherwise, professional diagnostics are needed to identify the fault source.