Getting To The Bottom Of A Rough Idle in Cold Weather

It's happened to almost everyone at one point or another: your car is running well all summer long, and then everything seems to fall apart once winter arrives. As the cold weather rolls in, many automotive problems may begin to stir from their summer slumbers. One of the more common complaints that mechanics run into is the "winter idle." If your car has suddenly begun to idle poorly in the low temperatures, then it may be suffering from this aptly named condition. There isn't just one single thing that always causes the cold weather shakes, but this article will help to point you in the right direction when youre

Start With Some Basic Diagnosis

Remember that the key to diagnosing any problem with your car is repeatability. It is imperative to discover the exact conditions that lead to a problem so that you can fully describe your symptoms to a mechanic. For cold weather idle problems, try to focus on when the rough idle begins to manifest and how long it lasts. Ask yourself these questions:

  • Does it only occur when temperatures outside are unusually cold?
  • Is the rough idle more prominent or only present when starting the car?
  • Does the idle seem to smooth out as the car warms up?
  • Does the car eventually reach its normal operating temperature after driving for a bit?

Zeroing in on the details of your idle issue is the first step to getting it fixed. If necessary, keep notes so that you can present this information to your mechanic for a quicker diagnosis.

Get Your Codes Read

Even if your check engine light is not on, you may have pending trouble codes stored in your computer. Your car's computer stores a code when it detects trouble, but it won't illuminate a warning light unless the problem happens repeatedly. An intermittent rough idle may not be enough, so having your codes read can help to shed some light on the issue. If you don't have a code reader, most auto parts stores will read the codes for you for free.

Understand the Likely Causes

Once you are armed with some diagnostic information and your engine's trouble codes, you can begin to look into your problem more seriously. While there are many potential causes for shaky cold-weather performance, two of the most common are failing engine temperature sensors and bad thermostats. In both cases, the underlying reason for a rough idle is an overly rich air to fuel mixture.

When your engine is cold, the computer uses a combustion mixture that is richer than usual. A thermostat that has failed to "open" will prevent your engine from warming up, and a temperature sensor that has gone bad may prevent your car's computer from realizing that the engine is up to temperature. In both cases, your fuel mixture runs rich and your idle will be rough.

Getting It Fixed

Most rough idle problems are not expensive to fix, and the costliest part is often the diagnostic effort that goes into finding the actual cause of the problem. By understand the likely causes of your rough idle, you can perform some essential diagnostic work yourself and provide your mechanic with the information they will need to get your car diagnosed and fixed more cost-effectively.

Contact an auto repair shop to learn more.