car shakes at idle but smooths out while driving

Have you ever experienced that your automobile shakes while idling or stopped but doesn’t while driving? Or have you at least heard someone complain about such an incident? It can be really depressing, particularly if you have no idea what might be wrong. Even though it might appear unusual, this condition isn’t as unusual as you might believe.

Rather than attempting to determine why a car vibrates when accelerating, it is far simpler to diagnose a car that shakes while idling but not when travelling. This is because the engine is the only moving component in a stopped vehicle. The great news is that you can be sure that this problem is caused by the engine and therefore, you can concentrate all of your repair efforts on that region.

Reasons Why Your Car Shakes When It Is Stopped and not while moving

1. Clogged Fuel Injectors

Fuel injectors, in particular, start to clog up with carbon buildup, varnish, and other sediments over time. As a result, fuel is provided inequitably with each operating cycle. When this occurs, the continuous supply of petrol or diesel to the combustion chamber is halted, causing your vehicle to shake or vibrate while it is idling.

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Fuel injectors that are clogged need to be cleaned or, in the worst situations, replaced. Utilizing a decent fuel injector cleaner will usually solve the problem. If not it’s always advisable to hire a mechanic. 

2. Worn-out Spark Plugs

The tiny electrodes known as spark plugs are what provide the high-voltage electric spark that is needed to ignite the engine’s fuel. The voltage-transforming mechanism loses its effectiveness when any of the spark plugs get unclean, melted, or worn out. As a result, the voltage decreases, and the spark plugs are unable to effectively ignite the fuel in the cylinders. This could result in the engine exhibiting misfiring, or it may shake while idling.

Replace your spark plugs if you haven’t done recently which would often make things right. Make sure you obtain the right spark plugs because there are numerous varieties. For exact specifications, you better read the manual of your vehicle.

3. Loosened Vacuum Hose

The vacuum hoses in a car facilitate the elimination of fuel-derived exhaust gases. When working on your vehicle or while driving, the vacuum hose inside the engine could suddenly disconnect or come loose. As a result, the engine may shake, rattle, and maybe even stop completely.

A similar shaking could be brought on by a hose crack or tear but to a smaller degree. Make sure all hoses are firmly fastened and you must replace a hose if it appears to be loose. Tiny air leakages are the most difficult to locate. In such circumstances, you can run the engine while spraying some soapy water down a hose. If there is a crack, the soapy water will momentarily stop the leak, and the idling shake will vary.

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4. Damaged Timing Belt

The timing belts provide the resistance needed to hold the camshafts of the engine in place. Your vehicle may shake while idling if the timing belt (serpentine belt) is strained, cracked, or torn. In such situations, it could be a potential sign of an upcoming timing belt failure that you should be aware of because your engine could sustain severe harm if your timing belt totally fails.

Although changing a timing belt usually entails changing the water pump as well, delaying doing so could result in hundreds of dollars in damage.

5. Dirty Air Filter

Your engine may vibrate when idling and not operate as smoothly as it should if your air intake is blocked. When the air filter of the engine is dirty or congested, the combustion chamber does not receive enough air, which results in insufficient fuel injection. It can cause the normal RPM to drop causing the vehicle to shake when it is stopped.

Luckily, changing an air filter is a DIY job and new filters are really inexpensive. Also, cleaning the filters is also an option.

6. Blocked Fuel Filter

Injectors won’t receive enough fuel from the fuel pump if your filter is jammed. Given that insufficient fuel is being delivered to the engine, this will result in shaking while the vehicle is idling.

The only option is to replace the filter and is advisable to be done with professional supervision.

7. Defective Motor Mounts

One of the motor mount’s purposes is to reduce the engine vibration so that passengers in the vehicle won’t notice it. Therefore, the damaged motor mounts will become evident very easily. While shaking and rattling at idle is fairly noticeable, a damaged motor mount will be more obvious when the engine is on and accelerating.

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If a faulty motor mount is suspected, it’s better to consult a professional and get it fixed because it may damage other parts of the engine as well.

8. Damaged Mass Air Flow Sensor

A malfunctioning air flow sensor can be the cause of your vehicle shaking while it is stopped, albeit this is probably the least significant cause. Its job is to accurately calculate the air-fuel ratio sent to the engine, so if it malfunctions and sends the wrong information to the vehicle’s system, the engine may receive the improper amount of fuel at the wrong time.

Conclusion

Driving a vehicle despite having shakes at idles could be risky depending on the fault in the engine. If it is due to a faulty timing belt or damaged motor mounts it could cause severe damage to the engine if it was left unchecked. Also, some causes could result in misfires which could be risky. Therefore, it is always better to have your vehicle checked and repaired if shaking is observed during idle to prevent more serious issues in the vehicle.

FAQ

1. Is it normal for a car to shake a little when idle?

It’s completely abnormal. A vehicle shouldn’t shake when idle. If shaking is noticed it’s probably due to an issue in the engine and must be checked as soon as possible.

2. What’s the use of spark plugs in the engine?

These are small electrodes which provide the high-voltage electric spark that is required to ignite the engine’s fuel.

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