White smoke from the exhaust when idling: What is the situation?

Randy Worner

Is the white smoke coming out of your car from car exhaust when you idle? Is this smoke dangerous and does it cause any problem?

Usually, there is nothing to worry about if that is the case. However, the white smoke can be a sign of an underlying serious issue that might require immediate attention.

In this article, we will discuss some of the common causes of white smoke when idling and show you possible fixes that you can apply to troubleshoot this problem.

What causes white smoke from the exhaust when I idle my car?

what causes white smoke from the exhaust when I idle my car
White smoke from the exhaust can be a sign of an underlying issue. When idling your car, white smoke released means that some engine-related part is malfunctioning. Thus, you need to have your car checked to prevent further damage.

Cracked intake gasket

A head gasket is a thin metal sheet that separates the upper and lower engine blocks. It seals the two sections, thereby preventing coolant leaks from the covers surrounding the engine. The common causes of intake gasket failure include wear and tear. It can also be caused by engine overheating if it is not sufficiently cooled.

A cracked intake gasket no longer keeps coolant within the channels, making it move down to the cylinder heads. Then, coolant burned in the cylinder head produces white or grey smoke, depending on the extent of damage. Thus, the cracked intake gasket should be replaced.

Faulty electronic control unit

A glitch in the vehicle electronic control unit (ECU) causes inappropriate timing of the injection. As a result, more fuel than necessary can flood the cylinders. Unburned fuel turns into white smoke, which you will see coming out of the exhaust.

White smoke from the exhaust when idling triggered by ECU error requires resetting of the unit. This can be done by plugging out battery clips for a few minutes and then reconnecting it. If the problem persists, you can see a mechanic with an automotive diagnostic tool to know the exact cause of the problem.

Faulty fuel injector

Fuel injectors control the passage of fuel into the combustion cylinder. If they are leaking, stuck in the open position, or malfunctioned in any way, there will be an imbalance. Excess fuel in the engine chambers is burned and expelled as white smoke through the exhaust.

Another common fuel injector problem is clogging. When that happens, the efficiency significantly decreases. You should let a mechanic check the injector problem and recommend the fix. To avoid faulty injector problems, regularly replace your filters.

Cracked engine blocks or cylinder heads

It is rare for an engine block to develop cracks. When it does, the repair is costly and time-consuming. However, it is the unlikely cause of the white smoke you see at the exhaust of your car when idling. Indeed, it is a rare occurrence, only seen in one out of hundreds of cases.

A cracked engine will reduce the performance of your vehicle. That is because the compression in the combustion chamber cannot occur efficiently. This leads to incomplete combustion, which causes the white smoke. Also, any damage to the cylinder head will cause a coolant leak. A mixture of coolant and oil burns in the cylinder to produce the white smoke.

What should I do?

For a DIYer

If you are a DIYer or have some mechanical skills, you can diagnose the cause of white smoke in the exhaust when the engine is idling. By just following the troubleshooting procedure, you should know the cause of the problem and fix it. In many cases, you need to replace the defective parts. Commit to it only if you are knowledgeable.

how to know the cause of white smoke from the exhaust when idling for DIYers
A DIYer can perform the procedure to determine the exact cause of white smoke in the exhaust when idling.

For a non-DIYer

Some of the suggested troubleshooting and fixes require technical skills. If you are a novice, take your vehicle to a mechanic for a quick check-up.


Proper vehicle maintenance can help prevent the problem of white smoke coming from the exhaust. Using the appropriate coolant and regularly replacing the filters will ensure your engines operate under optimum conditions. Take the necessary action as soon as you see the problem of white smoke appear to avoid further damages. Book an appointment with your mechanic and have your vehicle checked and fixed.

READ MORE: Why is my “check engine” light flashing and my car shaking?

Leave a Reply

Your email address will not be published. Required fields are marked *