Erratic or High Idle After Cleaning Throttle Body on INFINITI I35

The throttle body for the Infiniti I35 is known for carbon buildup, and requires regular, light cleaning to maintain peak performance. After cleaning the throttle body, many owners notice a very high idle, erratic (bouncing) idle, and unpredictable power surging.

The cause is normal ECU adaptation: When the throttle body builds up carbon, the rate of airflow is slightly decreased. The vehicles computer reads this decrease in air volume, and adjusts the throttle body settings to maintain the proper engine idle speed. When the carbon is cleaned out, the ECU now registers too much air, and cannot adjust back to the original settings. While it is trying to change settings, the idle will bounce from low to high, and the car will surge forward at times.

It has been recommended to simply wipe inside the throttle body every 12,000 miles, and never to touch the flap inside. Also, the cleaning procedure may be best left to a qualified technician.

The solution can be as simple as disconnecting the battery for at least an hour, having the dealer reset the computer, or, in extreme cases, replace the throttle bodies.