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Vehicle Shaking at Idle? Here Are the Most Common Causes and How to Fix Them

When starting up your vehicle, the engine should run smoothly and quietly. However, after years of racking up miles, it may start shaking and become noisy. We look at the most common causes and how to fix this issue.
Engine Vibration 6 photos
Photo: Orkun Azap on Unsplash
Spark PlugsA Spark PlugEngine MountsPetrol Fuel InjectorsHead Gaskets
Since winter is here, cold starts can reveal problems that were not that evident in the hot summer days. That’s mainly because the engine takes more time to heat up during the cold season. If your car starts shaking and the engine feels like it's going to fly off its mounts, here is what you should look for.

Worn Engine Mounts

Unless your car is a Ferrari F50, the engine does not sit directly on the chassis. To minimize vibrations, engine mounts are placed between the chassis and the engine.

They are usually made from semi-flexible rubber, which wears out in time leading to increased engine vibrations that are noticeable at idle.

Engine Mounts
Photo: ZF Friedrichshafen AG
Replacing them is not an easy task, so we recommend taking the vehicle to a dealership or your nearest mechanic. Choose high-quality OEM or aftermarket parts to avoid having to replace them again in a couple of years.

Problems With the Ignition System

Each cylinder uses one or two spark plugs to ignite the air-fuel mixture, and over time they deteriorate to the point where the mixture no longer ignites properly.

Whether your car has one or multiple ignition coils, these should also be checked. They may not deliver enough voltage to the plugs, leading to weak combustion. Spark plug wires and the ignition coil unit could also be faulty, so they need to be checked as well.

If you never properly serviced the ignition system on your aging vehicle, now is the time to do it. Start by replacing the spark plugs and have a mechanic check the state of the coils, wires, and control unit.

Poor Compression

When the engine is running, the ignited air-fuel mixture expands, and the piston is forced downward, rotating the crankshaft. But if one cylinder leaks, it will result in poor compression, which in turn translates to an unbalanced engine and increased vibrations.

Fixing this is a little more problematic and may require a full engine disassembly, but most times, just replacing the head gasket may solve the issues.

We also recommend that your mechanic checks the state of the valves and piston rings and have them replaced with quality parts.

Faulty Fuel Injectors

Petrol Fuel Injectors
Photo: Robert Bosch GmbH

These are critical parts of the engine that deliver a precise amount of fuel into the cylinder, but due to extensive use and contaminants, they eventually stop working properly. This leads to an unbalanced engine or a cylinder misfire, which may be the cause for that awful idle shaking.

Injectors can be cleaned using several types of additives, but this is only a temporary solution. They need to be checked by a professional and either refurbished or replaced. Unfortunately, especially on diesel engines, fuel injectors are expensive.

Clutch Problems

If your car has a manual gearbox, the clutch might be dragging or not fully disengaging. This may be caused by a hydraulic leak, a worn cable, or a faulty master cylinder.

This will produce an extra load on the engine, causing an increase in vibrations when idling. A comprehensive check of the clutch system is required, which might lead to the replacement of several components.

Increased engine vibrations may be caused by other components as well, but these are the most common problems which result in this annoying symptom.

As an obvious conclusion, an older vehicle requires more attention than a brand-new one. To avoid expensive repairs, it’s best to routinely check the engine and replace worn out parts as soon as the first symptoms appear.
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About the author: Vlad Radu
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Vlad's first car was custom coach built: an exotic he made out of wood, cardboard and a borrowed steering wheel at the age of five. Combining his previous experience in writing and car dealership years, his articles focus in depth on special cars of past and present times.
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