I had a check engine code erased by AutoZone on my car, right as they finished I went driving and noticed the unusually low idle RPM's, looked like under 500. It felt like the car wasn't running it was so low, but it was. Then after driving the car, idle rpm's went back to normal. Does the computer adjust itself after sometime? Why did it get so low anyway?



99 LX coupe 5-speed

 

Yes it does. Due to variances in the different sensors, the ecu has to learn their normal values before it can determine where to set the idle. When they cleared the codes they also cleared the learned values it needed to determine idle speed. The easiest way to get it back is to do the idle learn procedure: Warm the engine up to normal operating temperature, then let it idle with all loads turned off for 10 minutes.