Resetting IAR in 2006 Nissan Altima with erratic idle

Recently in our Ask a Mechanic forum, WJH asked about his 2006 Nissan Altima, which is having erratic idling issues.

Although his particular problem is actually a little more in-depth, this issue is common when the engine throws a code relating to the Air Idler Control (AIC) or when the AIC has been replaced without doing a proper Idle Air Relearn procedure (IAR). Often this is done in conjunction with or because of failed or faulty oxygen and/or temperature sensors.

The IAR procedure

Most quality maintenance and repair manuals will have this procedure spelled out and it is generally the same on most vehicles equipped with an AIC. It may vary by manufacturer and model year, however, so the following specific to the 2006-generation Altima. Check a manual specific to your vehicle before proceeding.

First, the car must be at full operating temperature. Run it until it reaches that before continuing.

Once at operating termpature, idle should "average" about 700 RPM (since it's fluctuating, this may be difficult to determine, so go by engine temperature instead). Turn off all electrical accessories (lights, headlamps, air conditioning, radio, and so forth).

Turn off the engine and wait for ten seconds. Turn the key to the "on" position without starting the engine. Wait for another three seconds.

Within five seconds, fully press and release the accelerator (gas) pedal. This can be timed by counting "one one thousand" to mark a second and pressing the pedal and releasing on every other syllable - "one" (press), "one" (release), "thousand" (press), "two" (press)..

After five press and releases, press the pedal all the way down and hold for seven seconds. Two to three seconds after that seven are up, the engine service warning light should begin blinking.

Keep the pedal held down and wait another ten seconds and the light should stop blinking. As soon as it stops, release the pedal.

Start the engine and watch the idle and check that it's still at operating temperature. The idle should be at around 700 RPM (the car's normal "resting" idle). Let it run for half a minute or so, then rev the engine a few times, jumping it up to 2,000 or more RPMs and letting it drop back to "rest" at 700.

Your car should now operate normally assuming no other problems are present.