As a car owner, you might worry about discovering a mechanical problem as you drive. But one common symptom of possible trouble involves changes in the way your car’s engine idles while braked or parked.
Since unusual idling performance can occur for a variety of reasons, you should understand this symptom so that you can seek the appropriate fix for it. Consider the following four idle abnormalities and their potential causes.
1. High Idle Speeds
You may come to a stop and realize that, instead of your engine settling down into its usual low idle, the engine continues to rev as if you’d applied the gas. In many cases, an abnormally high idle while stopped stems from faulty instructions. You may have a malfunctioning fuse, idle air control (IAC) motor, or computer.
Exhaust and ignition problems can cause an engine to idle at an unusually high level. Examples include a dirty throttle body, a leaky vacuum hose, and a cracked air intake tube. You might also have an alternator issue. If your dashboard indicates abnormally high engine temperatures, the overheating could raise the idle level.
2. Intermittent or Uneven Idle
Normally, a car idles at a smooth, steady rate when its engine receives a consistent mix of oxygen and fuel. If your engine has a clogged, dirty engine air filter, it may idle roughly while also burning more gas than usual. A leaky positive crankcase ventilation (PCV) valve can also impair the fuel-to-air mixture.
Bad spark plugs or spark plug wires can cause an engine to idle roughly. Although modern spark plugs can last a long time, as they age they can get fouled by carbon deposits or develop electrode wear that widens the gap that the spark must travel for proper combustion. Your mechanic can replace these parts easily.
If your car’s engine revs up and down repeatedly but only when you have the air conditioner engaged, the AC may have a problem that causes it to place unnatural strain on the engine. A worn-out compressor or compressor belt, faulty AC cycling switch, or incorrect refrigerant level can trigger this symptom.
3. Rattling Noises
If your car insists on making rattling noises when idling, you may have nothing more to worry about than a loose cabin component. Even well-designed, well-built cars can suffer from this problem over years of everyday use. You may need to have your center console or glove box hinge, or trunk latch tightened.
The parts attached to your car’s undercarriage can also shake themselves loose, creating annoying rattling noises at idle. Possible culprits include the heat shield, muffler, tailpipe, exhaust system clamp, and catalytic converter core. Since these components have a direct effect on your car’s function, get them fixed as needed.
Don’t forget to check the components under your hood. A car can rattle when idling due to failures in an engine valve’s hydraulic lifter. An ever-growing gap between a piston’s walls and its surrounding cylinder can cause a rattling sound known as a piston slap.
4. Unusual Vibrations
Many of the same exhaust system and ignition problems that cause abnormal idling speeds, such as bad spark plugs or vacuum hose leaks, can make your car shake or vibrate. However, two other underlying failing components can also call attention to themselves in this manner: the timing belt, and the motor mounts.
A car’s timing belt ensures proper engine timing for smooth operation. If your car vibrates when idling and you’ve never had it changed or adjusted, your auto repair team may need to tension the belt or even replace it entirely to restore normal engine timing.
Motor mounts hold the engine firmly in the engine bay to minimize and dampen vibration. If these mounts start to give out, your engine will shake noticeably.
Don’t ignore a change in the way your car idles until the underlying cause has gotten out of hand. Instead, let the experts at White’s Automotive Center diagnose your problem and perform the necessary repairs to restore smooth idling performance. Contact us today for more information.
