Q&A

 Master

This issue is related to the loss of battery power to the powertrain control module (PCM). Here is what happens, over time deposits build up in the throttle body which slowly begins to restrict the air flow to the engine at idle. The PCM compensates for this by increasing the air flow via the idle air control valve. This happens very gradually over time and you never notice a thing - until the battery is disconnected. When the PCM looses battery is idle speed memory is also lost. There are two ways to restore the proper idle speed on your 2003 Chevrolet Trailblazer. One, over time the PCM will "relearn the correct idle - this should not take very long and you may have already noticed an improvement. You can speed up this process by letting the engine warm up and idle for about a minute, then place the transmission in drive with your foot on the brake for a minute, lastly turn on the A/C with the transmission in drive with your foot on the brake. The second option would be to remove the air intake at the throttle body and clean the throttle deposits using some brake cleaner and a shop towel.