Can A Bad Water Pump Cause Rough Idle?

Can A Bad Water Pump Cause Rough Idle?

Yes, it can. However, a bad water pump does not cause rough idle directly. It causes rough idle indirectly, through the leak of coolant.

Aside from rough idle, a bad water pump can also cause whining sounds, a rise in engine’s temperature, create holes in the water pump, car running on low coolant, loose pump pulley, and steam coming from beneath the hood.

How does a bad water pump cause rough idle?

On the contrary, several things can cause rough idle, apart from a bad water pump. These include dirty fuel injectors, vacuum leak, clogged air filter, fouled spark plugs/spark plug wires, failed exhaust gas recirculation, bad airflow sensor, and a worn-out oxygen sensor.

In this post, we will look at how a bad water pump can cause rough idle. On top of that, we’ll elaborate on other effects of a bad water pump and other causes of rough idle. But first, let’s find out how a bad water pump causes rough idle.

How Does A Bad Water Pump Cause Rough Idle?

Coolant Leak

The most common way a bad water pump leads to rough idle is through a coolant leak. When you’ve got a coolant leak, much coolant may be lost, which may cause the engine to overheat. As a result, this makes the head gasket leak and cause rough idle.

If there is a coolant leak, you should take your car to the mechanic to fix it or replace the pump with a new one. It is advisable to change a water pump after covering at least 60, 000 to 90, 000 miles, which is around the same time as the timing belt.

It is essential to check if your car has a leakage of any kind before it gets out of hand. A prolonged leakage can cause other severe car problems such as rough idle and much more.

The Rise In Engine Temperature

Another issue that can indirectly instigate a rough idle because of a bad water pump is its temperature rise. If the engine’s temperature rises because of a bad water pump, this can also lead to rough idle. High temperatures affect the oxygen sensor, which in turn causes rough idle.

The oxygen sensor is part of the car’s emission system. If it is affected, it will not have the right air-fuel balance for efficient and clean combustion. In the end, it may send wrong information to the vehicle’s computer.

As a result, the engine may run too lean or too rich. If it is too lean, then it will cause rough idle. But if it’s too rich, it will lead to poor fuel economy.

What Is Vehicle Idling?

This is when the car has enough power to run car parts such as the steering wheel and the alternator, but not enough power to move the vehicle. When a car is idling, it displays below or above regular speed. Also, it can have irregular revolutions per minute (RPM).

For instance, a typical sedan should have an average idle speed of 600 and 1000 RPMs. So, if it’s above or below these RPMs, it is rough idling.

See Also: 4 Causes Of Car RPM Fluctuation While Driving

What Are The Other Causes Of Rough Idle?

Clogged Air Filter

If you have a clogged air filter, it will reduce airflow into the engine, resulting in rough idle. The work of the air filter is to keep dirt, dust, and other debris from accessing the engine. In this case, you can clean the clogged air filter, or if it’s damaged, then you should replace it.

Dirty Fuel Injectors

When the fuel injectors are clogged from carbon, they make less fuel to go through the injectors; thus, causing poor performance and rough idling. If the fuel injectors are dirty, you can remove them and clean or take to your mechanic.

Fouled Spark Plugs

If the spark plugs or spark plug wires are fouled, they will not produce the required amount of power, which will cause rough idle. Sparks plugs have to be changed after a specific period for them to work effectively. Most cars need their spark plugs to be changed after 20, 000 to 50, 000 miles.

Worn Out Oxygen Sensor

Oxygen sensors are critical parts of the engine. They maintain the right air-fuel balance for efficient and clean combustion. If the oxygen sensors are covered with carbon and can’t function properly, they will make the car rough idle.

Failed EGR Valve

Another vital part of the engine that has to be maintained is the exhaust gas recirculation valve. This component plays a crucial role in keeping the vehicle’s emissions lower. However, this part may also fail to open or close, leading to a lean air-fuel mixture that causes rough idle.

Can a Bad Water Pump Cause Rough Idle

What Is A Vehicle Water Pump?

A vehicle’s water pump is a part that makes sure the coolant keeps moving via the engine block, radiator, and hoses to maintain an ideal operating temperature. If this part fails, it will affect all the parts that the coolant passes through. Also, it will affect the adjacent parts as it will also have an impact on them.

A bad or failed water pump has several effects, including engine overheating, rust and corrosion on the pump, damaged bearing, deposit build-up on the pump, and causes coolant leakage.


Even though a bad water pump causes rough idle, it does not cause it directly. Instead, it causes rough idle by affecting other parts of the engine connected to the water. Effects of a damaged or bad water pumps such as leaking coolant and engine overheating cause rough idle.

That’s why you have to constantly inspect your vehicle or take it for maintenance to avoid costly repairs. A bad water pump might not only result in rough idle but also cause your engine to overheat, coolant to leak, steam to come out, and make the car to produce a whining sound.

We hope you will always inspect your vehicle and have it in tip-top conditions to avoid such issues!