car idles rough but drives smooth

Car Idles Rough But Drives Smooth

If your car idles rough but drives smooth, it is okay but not fine. Confusing right, a normal car should idle and drive smoothly, this virtue proves that the engine performance is okay.

If you have new car you are definitely might not know how a rough idling car feels like except if you have experienced it with before. However due to usage and age some of the engine and overall car parts begin to wear off there by failing to perform there functions appropriately.

Rough idling can be in two forms, either your idling rough and driving smooth or idling rough all the way. Whatever the case maybe, they both share some common causes of rough idles.

Read Also:- 10 Common Signs of a Blown Head Gasket

Common causes why your car idles rough but drives smooth

Idling itself is the rate at which the engine operates when it is not driven or engaged in gear. A better picture of and idling car is when you have just started you vehicle in the morning and you are not raving it or when parked to quickly get something but the engine is running.

Below are common causes of why you truck, van or car could be idling rough. Continue reading to find out

  • Failing spark plugs                                                                                                                                                                                                                                                                                                                          A bad spark plug can be very notorious to detect sometimes as it needs very close attention and monitoring to tell if is the spark plug or spark wires. Either the spark plugs or spark cable connected to the spark plug could be the cause of rough idle.                                                                                                                                                                                                                                                                                Spark plugs are responsible for igniting sparks in the combustion chamber enough to make the mixed fuel and air to burn thereby producing energy. Spark plugs are usual cause of an idling rough engine.                                                                                                                                                                                             When enough sparks to ignite the engine are not produced by the spark plugs, fuel mixed with air in the combustion chamber would not burn as expected. When fuel mixed with air is not burnt well, there would no production of enough consistent energy for the engine to run thereby causing a rough idle.
  • Worn engine mount or engine seat                                                                                                                                                                                                                                                                                          Most likely, this would not apply to new cars, trucks and vans, as everything is expected to be new. In older vehicles engine seat or moto mount could be the reason why your car idles rough but drives smooth.                                                                                                                                                                                       Engine mounts, also known as motor mounts, are designed to secure your vehicle’s engine and transmission to the subframe. They are also intended to absorb vibration and shock to ensure that the driver is unable to feel any movement of the motor.                                                                                                                                                                                                                                                                      Like any vehicle part, however, the engine mounts can go bad. Signs of a bad moto mount includes car jerks, unusual vibration, rocky start and impacted noise.
  • Vacuum Leak                                                                                                                                                                                                                                                                                                                            Under the hood are many hoses that snake around the engine. These hoses are meant to create a vacuum seal for the air and fuel controlled by the throttle to regulate air flow and engine speed and vacuum within the intake manifold.                                                                                                                                                                                                                                                                                                                  After a few years and exposure to extreme temperatures, the rubber hoses wear down and develop leaks. When too much air is added to the air/fuel mixture it can cause misfires, rough idle, and an increase of RPMs. Have a technician inspect your vehicle’s hoses regularly for cracks, breaks, or dryness and replace every 50,000 miles.
  • Clogged fuel injectors                                                                                                                                                                                                                                                                                                                    Fuel injector can get clogged or even blocked over time as a result of dirty and tin carbon filings present in the fuel or fuel line. The fuel injector it responsible for delivering fuel to the combustion chamber for aid combustion.                                                                                                                                                                                                                                                                                                                                  The injector performs its function through specially designed valves that can open and close within a second. The main function of the injector is deliver fuel to the combustion chamber.

Any of the above mentioned faulty engine parts can be the reason why your car idles rough but drives smooth. Even you can do almost nothing to fix rough idles as an average driver or car owner, it is good to have and idea before going the mechanic.

Will a vacuum leak cause rough idle?

If any of these hoses spring a leak, a lean air/fuel condition will result, causing a rough idle from the resulting engine misfire. Vacuum leaks can also be caused by leaking intake manifold gaskets, vacuum brake boosters or vacuum supply tanks.

After a few years and exposure to extreme temperatures, the rubber hoses wear down and develop leaks. When too much air is added to the air/fuel mixture it can cause misfires, rough idle, and an increase of RPMs. Have a technician inspect your vehicle’s hoses regularly for cracks, breaks, or dryness and replace every 50,000 miles.

What are signs of a vacuum leak?

Symptoms of a vacuum leak include the Check Engine light, rough idle, stalling and a hissing sound coming from the engine bay. The engine may run well at higher RPMs, but surges, runs rough and struggles to maintain stable RPMs at idle. Often, the engine stalls when stopping.

What causes a car to shake while idling?

Worn-out seat engine or motor mount can be a major cause of your car shaking or vibrating when driving. Failing spark plugs are not left out either, this device can be the culprit are very notorious in causing your car to shake sometimes.

When spark plugs are covered by soot they ten to give less sparks or loss there ability to spark. If spark plugs looses there sparks they fail to produce enough spark to ignite the the fuel mixed with are in the engine.

Worn-out motor mount are not left out among the cause of shaking vehicles. Engine mounts are the component responsible for securing the engine of a vehicle to the chassis.

If either the motor mount or the spark plugs are faulty, they can easily cause shaking abnormalities. You should consider replacing them as quick as possible to avoid causing further damages.

Can a bad air filter cause rough idle?

Can a bad air filter cause rough idle? Yes is the direct answer to this question but let me explain how air filter works. Air filter is responsible for cleaning the air that is being delivered to the engine.

Funny right? Yes the engine breaths in air too just like you do and it breaths in clean air. A dirty air filter reduces the amount of clean air that is getting through to the engine, decreasing its power and performance.

So the bottom line is, if your car’s air filter is dirty it will directly impact your engine performance. Symptoms of a bad air filter includes reduced horsepower, black, sooty smoke or flames exiting the exhaust and smell of gasoline when starting the car.

Remember, a failing spark plug or a dirty air filter could be reason why your car idles rough but drives smooth. If you have any questions please ask us using the comment section below we will be glad to answer.

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