Is it normal for the engine to shake at 800 rpm idle but smooth out at 1000 rpm?

[SanWillow]

This is not a normal situation. Once the engine exhibits such issues, it's necessary to check whether the idle speed motor is malfunctioning. Engine shaking at idle can lead to increased fuel consumption during vehicle operation, unsteady acceleration, and carbon buildup inside the engine. Here's relevant information: Increased carbon deposits should not be allowed with prolonged idling. Keeping the vehicle idling for extended periods will cause more carbon buildup in the engine, resulting in reduced power during driving. The normal idling duration for a vehicle is 3-5 minutes. If it exceeds this time, the vehicle should be turned off. Normal idle speed: The standard idle speed is around 750 rpm. If the engine speed drops below 750 rpm during idling, the vehicle is prone to stalling. If the idle speed is too high, it will increase fuel consumption. You can determine whether the vehicle is operating normally by observing its idle speed value.

[Wood]

I recently experienced a similar issue when driving my friend's SUV. At an idle speed of 800 RPM, the steering wheel noticeably vibrated, and the body shook slightly, which was quite alarming. However, as soon as I lightly pressed the accelerator to reach 1000 RPM, the shaking disappeared completely. This is definitely not normal. I think common causes might include ignition system problems, such as aging spark plugs leaking electricity or poor contact in the ignition coils. Another possibility could be excessive carbon buildup in the engine, affecting combustion efficiency at idle. Dirty fuel injectors causing uneven fuel supply can also lead to this issue. If you frequently idle for long periods while driving, carbon deposits can accumulate faster. If left unaddressed, fuel consumption may increase, and over time, it could lead to internal engine wear. I recommend first checking the spark plugs yourself—they're quite simple to replace. If there's no improvement, then take it to a professional shop to read the fault codes for diagnosis. Don't delay; safety comes first.

[Angelina]

As an experienced road-tripper, I understand your concern. The car noticeably vibrates at an 800 rpm idle, but smooths out when accelerating to 1000 rpm - this phenomenon isn't uncommon, but it's not normal either. It's likely an issue with the idle control system, such as severe carbon buildup in the throttle body restricting airflow, or worn engine mounts reducing vibration damping. My previous car had similar symptoms - after cleaning the throttle body and intake pipes myself and replacing the spark plugs, it improved significantly. During routine maintenance, regularly inspect these components; frequent highway driving actually helps reduce carbon buildup. Ignoring it may worsen vibrations and even affect acceleration performance. Addressing it early saves trouble - buying a tool set for DIY repairs can solve it.

[GenesisRose]

I think this issue is worth being cautious about. Severe shaking occurs at an idle speed of 800 RPM, but it returns to normal when the speed increases to 1000 RPM. This is mainly because the engine combustion is unstable at low speeds, such as uneven fuel supply in the fuel system or air leaks, while higher speeds provide a more adequate combustion environment. Common causes include insufficient fuel pump pressure, dirty fuel injectors, or carbon deposits inside the engine interfering with cylinder operation. You should always choose reputable gas stations for refueling, as poor-quality fuel can easily lead to carbon buildup. If you notice this issue, investigate it promptly. Check if the air filter is clean, and getting it repaired isn't expensive either.