Car vibrates when idle and AC is on. If you’ve noticed your car vibrating when it’s at idle and the air conditioning (AC) is turned on, you’re not alone. This peculiar issue can be a cause for concern and may leave you wondering about its origins and possible solutions.
Hearing odd noises or experiencing vibrations from our car usually means that some mechanism is chugging. The symptoms and causes are extremely varied, it can be hard to distinguish what’s going on.
‘Car Vibrates When Idle And AC Is On’
As mentioned above, issues differ greatly.
Hence why covering their general symptoms is useful. The causes are often found all across the vehicle but the most notable ones require specific coverage.
Keep in mind that the effects of the causes may not be limited to the issue of the car vibrating when idle and ac is on, other symptoms may also crop up to reinforce the suspicion of a certain component malfunctioning.
- Engine Load
The issue of the car vibrating when idle can come from our engine being strained in its function. As you can imagine, an air conditioner requires quite a bit of work to operate. Hence why our car will generally compensate while this feature is running. This compensation then leads to the sound we hear. 
Specifics of the matter tie into the way the engine attempts to regulate said strain. When additional components are activated, the car engine tries to compensate for the strain. These compensations include increasing the drag of the engine.
Unfortunately, this action can affect the idle compressor. When this item is thrown out of its usual operating procedure, the issue of the car vibrating while idle when ac is on can appear. In fact, there will be problems with steering even when the ac is off, which can make the problem quite a hassle to deal with.
- Engine mount issues
Continuing on from engine load we have another issue that can be caused by the engine. This one is the engine’s mount. The issue will end up causing the air conditioner to make an odd noise. The most common noise to hear is a clicking one. 
This comes from a number of things that wear at the mount of the engine. One of these includes the air conditioner itself. Just like we discussed in the engine load, this strain can make the engine perform worse. Eventually, the engine mount could dislodge itself and problems will escalate further.
- TPS malfunctioning
Another reason why our air conditioner could cause hassle to the car while idling can tie into TPS malfunctioning. TPS stands for Throttle Position Sensor, which is a sensor that monitors the air intake of an engine. 
The TPS will adjust the RPMs of our car in a way where the RPM correctly mirrors the position of the throttle. However, malfunctioning one will have issues providing that functionality.
As the control over RPM is hampered, we can expect the car to start shaking when AC is turned on. Though it doesn’t correlate directly to the ac, that extra strain can really show.
- Spark plug problems
There are more sources of the car vibrating while idle and ac is on. The spark plugs are next on the list when it comes to components that cause the issue. Though the problems that they cause for ac often extend to the entire car.
Spark plugs are meant to ignite the fuel inside of the vehicle. As we drive, it’s the spark plugs that cause the combustion with an electrical spark, hence their name. However, as with all components, they can wear out or break. 
When this occurs, our car will suffer numerous issues. A lack of connection during the early electricity generation is one that ties directly into the air conditioner operating correctly. Producing unwarranted vibrations due to failing spark plugs.
- Fuel injector problems
Continuing with the combustion system issues, we have faulty fuel injectors. A fuel injector injects fuel into the car engine which will then be mixed with air and ignited by the spark plug. However, if something goes wrong, the fuel may be improperly delivered or not delivered at all.
A fuel injector can malfunction in many ways. Whether it’s faulty or broken, the fuel injector will cause a car to rough idle just like all the other issues. The ac being on causes the issue to be even more present.
- Loose AC hose
The hoses within our car serve primarily cooling functions. Hence it’s no surprise that they have a role to play in this particular issue. Air conditioners’ weakest structural components are the hoses themselves.
Though made of flexible rubber, the high-intensity environment they operate within can put a lot of stress on the hose.
The result of said stress could result in a hose becoming loose or disconnected from the engine mount. Disconnected hose especially will cause the car to shudder whenever AC is turned on.
This problem is quite simple but often overlooked, as rough idling is something people generally assume comes from other components of the vehicle. 
Solutions to Car Vibrating When Odle and AC is On
No problem is without a solution. All of the issues can be resolved by switching out the old part for a new one but having other options for solving the issue helps too. Especially when certain replacement parts can get exceptionally pricy.
Spark plugs will have to be replaced. Thankfully, most of the spark plugs in cars are decently cheap to replace. Making the cost of this fix on the lower end. Though the best thing to do is make them last.
They may not be the most expensive but it will still cut into our funds. To prolong a lifespan of a spark plug, make sure to maintain the cooling systems of your vehicle as overheating is the main cause of early spark plug malfunction.
TPS-related issues of rough idling, while AC is on, can also be addressed with proper maintenance. This component will often be put in danger when the connection between it and the ECU is compromised.
That can come from many factors but corrosion and wearing out of their connections is the main one. Pay extra attention to potential damage here.
You may need to pay extra attention to the compressor and how it operates within the car. Spotting issues with it can be done through consistent inspections, which can aid any problem mentioned above. Giving us a head start on problems before they develop into something much more serious.
Make sure to test the fuel injection as well. While doing so, spark plugs can also be inspected. Considering how close the two components are in function, the malfunction on one could extend to the other.
Either one having issues can be a warning sign of wiring issues or connection problems.
Engine issues like load and mount are ones that are addressed quickly by the same approach as the others. Though you can also directly inspect the engine mounts for a confirmation of their potential malfunction.
This makes it easier to actually lower the number of possible issues and cut straight to the chase.
The hose of your AC getting disconnected is the easiest issue to prevent and solve. Going under the hood and tightening the hose’s connection is a surefire way to keep ahead of the issue.
Even when the problem springs up, this action is simple enough to perform with only the basic tools.
However, this doesn’t mean that you should ignore loose or disconnected hoses. Solve the issue quickly for maximum driving quality.
With all of these solutions covered, you should have a high chance of resolving the problem of rough idling while AC is on. However, the complexity of cars makes malfunctions hard to fully predict.
Although all of the aforementioned covers a wide variety of causes common to rough idling problems, there could still be others to take care of. If none of the immediate actions help solve the issue, it may be time for a more thorough check.
Read Also: Power Steering Malfunction Mercedes-Benz
The rough idling of a car can be an annoying issue. Reducing general comfort of the vehicle as we drive.
However, it only gets worse when tied to the operation of the air conditioner which also increases the comfort of the vehicle. Idling becomes annoying and the concerns about the cause of the issues mount.
As witnessed above, the issues are exceptionally varied. Though the idling and ac problems are almost guaranteed to appear, the issue will cause further problems.
For example, spark plugs and fuel injectors will impact the general driving experience as they wear out.
Thankfully, we can address a good number of these issues and prevent them from getting out of hand by following some simple fixes.
Read Next: Increased Steering Effort BMW