What Causes Engine Idle Shaking but No Shaking When Accelerating?

[VonBella]

The reasons for engine idle shaking but no shaking when accelerating are: 1. Changes in fuel injection quantity, causing the engine speed to fluctuate; 2. Malfunction in the fuel pump pressure regulator or sensor, leading to incorrect fuel injection correction signals; 3. Cracked vacuum booster pipe; 4. Carbon buildup or dirt on the throttle body, or incorrect throttle position sensor alignment. An engine (Engine) is a machine capable of converting other forms of energy into mechanical energy, including internal combustion engines (reciprocating piston engines), external combustion engines (Stirling engines, steam engines, etc.), jet engines, electric motors, etc. The term engine can refer to both the power-generating device and the entire machine including the power unit.

[LeEmilia]

I've been driving for over a decade and encountered similar issues. Engine vibration at idle but smooth acceleration usually occurs because the low idle speed makes engine operation unstable, while higher RPM during acceleration masks the problem. Common causes include: aged spark plugs or excessive carbon buildup leading to poor ignition; incorrect air-fuel ratio, possibly due to clogged fuel injectors; dirty throttle body affecting air intake; loose engine mounts causing resonance; vacuum leaks resulting in insufficient power. I recommend first checking spark plugs or air filters yourself and cleaning them. If no improvement, visit a professional shop for diagnosis. Regular maintenance like oil changes and throttle body cleaning can prevent these issues. Don't ignore it – idle vibration affects fuel economy and may damage the engine long-term. Simple repairs can fix it, so don't delay.

[DelEmmett]

As a car enthusiast, I believe the core issue of idle shaking that disappears upon acceleration lies in the sensitivity of idle conditions. During idle, the engine operates with minimal load and low RPM, making it susceptible to minor issues like faulty ignition coils, uneven fuel injection, or carbon buildup, which can cause vibrations. When accelerating, the higher RPM and more stable engine operation mask these problems. You can check if the spark plugs are worn out, try cleaning the throttle body deposits, or replace the ignition wires. Don’t forget to inspect the engine mounts for damage, as vibrations are more noticeable at idle. If you’re not comfortable doing it yourself, have a mechanic use a diagnostic tool to check the air-fuel ratio data. This issue can often be fixed with minor repairs, so don’t worry about high costs. Regular maintenance like changing the air filter and cleaning the fuel injectors can reduce the likelihood of it happening. Safety first—address the issue promptly to avoid problems at high speeds.

[VonHadley]

My car has been doing the same thing recently, shaking badly at idle but smoothing out when I step on the gas. I looked it up online, and it might be due to old spark plugs, too much carbon buildup, or a faulty sensor causing sluggish response at idle. Another possibility is dirty fuel lines – at idle, less fuel is injected, so the shaking is more noticeable, but when accelerating, the increased fuel flow masks the vibration. It's pretty annoying, but no need to over-worry. I'll take it to the shop for a check-up first, maybe the throttle body or ignition system needs cleaning. To prevent this, I should use fuel additives more often and change the air filter regularly. Better get it fixed early to avoid trouble on the road.