Why Your Car Isn't Idling Properly

When your vehicle is started, but is not in motion, the engine is still going, which is called idling. If you have a newer vehicle, your engine is probably so quiet that you can barely hear it idling. Older vehicles may sound a little louder while they idle. If you know your car well, you should be able to tell whether idles properly or not.

For those who aren't sure, when a car isn't idling properly, the engine may seem rough and it probably won't sound right. Your car engine will even shake and make sputtering sounds. If your car isn't idling properly, here are some possible reasons why.

Loose Vacuum Hose 

If your vacuum hose is leaking, it will result in poor engine performance and cause rough idling. The vacuum hose is part of a modern vehicle's fuel injection system that helps the computer in your vehicle's engine to calibrate the pressure of the fuel injectors.

When a loose hose causes a vacuum leak, the computer does not receive accurate information, which causes the engine speed to fluctuate. If you haven't replaced the vacuum hose on your vehicle for a while, this might be what's causing your rough idling.

In order to know for sure, simply pop the hood, and with the engine still running, listen for a hissing sound. If you hear it, take your vehicle to an auto repair shop to replace the loose vacuum hose.

Clogged Air Filter 

The air filter on your car protects your engine by catching dirt and other types of debris. When the air filter gets clogged, the air flow to your engine becomes constricted, which causes your engine to not run as smoothly.

Air filters should get replaced every 15,000 to 30,000 miles. However, if you drive on dirt roads, you should change the air filter more often. A good time to get your air filter inspected is during routine oil changes.

Spark Plug Problems 

Spark plugs may be little, but they help your vehicle to run smoothly and efficiently. Properly working spark plugs are directly linked to the performance of your car's engine. In most cases spark plugs should be changed every 30,000 miles.

If they are not changed when they need to be, deposits can build up, which causes an unreliable supply of energy to your engine. Spark plug wires and ignition coils can also malfunction, which also causes rough idling.

To alleviate this problem, change your spark plug wires every two years, and if you notice a check engine light on your dashboard, take your vehicle in, as this could indicate a problem with the ignition coil.

Other Common Reasons

Besides the ones listed above, here are some more reasons your car may not idle properly:

• Your vehicle's oxygen sensor, EGR valve, or PCV valve is failing to work properly.
• Your vehicle has over 100,000 miles on it and some of the engine components have excessive wear and tear.
• You have an older vehicle with a carbureted engine and carbon deposits have formed around the carburetor.

Because your engine may idle improperly for a variety of reasons, take your vehicle to a trusted auto repair service so that the problem can be correctly diagnosed. Professional diagnosis gives you the tools to repair your vehicle quickly so that your engine idles properly again.

No matter what the reason, if your car isn't idling properly, and you live in the Bay Area, our ASE-certified technicians at Letcher Bros. Auto Repair will run computer diagnostics on your vehicle to determine the problem. Contact us today for a free estimate or to schedule your vehicle for repairs.