2004 chevy aveo idles high while sitting still. 4000 rpm?

check coolant level if low tricks water sensor into thinking the engine is cold if full then the idle speed control motor is sticking.

i cleaned the egr valve on mine solved the problem

Not real sure but I found a link which may help
http://thechronicleherald.ca/wheelsnews/94544-qa-problem-with-throttle-positioning-sensor-how-well-do-today-s-fuels-work-in-60-s-

https://community.cartalk.com/t/chevy-aveo-revs-too-high-at-start-and-idle/56627

Your throttle position sensor is bad.

Did they check to see if any reprogramming or up dated software for the PCM is avilable ? Sometime computer gliches will cause problems an the dealer can do a reflash to fix the problem . Did they look at TSB - technical service bulletin .You could go to the GM TDS web site an enter your vehicle ID # or VIN an it will tell you if any updated software is available . Also could have a lose or corroded connection ,body grounds etc.... How to Program and Reprogram OBD 2 Modules Example Code P0326 Knock Sensor

the rpm is set by computer, is the ck eng light on, if so you may have a intake air leak causing high idle

Try hitting the brake off and on to see if the rpm changes when you do that with the car in park. If it does, you may have a ruptured brake booster. A fluctuating rpm while your car is in park with the brake on indicates a vacuum loss. Other things may cause a vacuum leak including the air conditioner controls inside the vehicle. Other things that cause this may be cruise control or your Air Conditioners high idle solenoid.

Check your throttle position sensor

I bought my 2004 aveo 49 miles. I've had several issues with the car. But recently I been experiencung high idle at start up and clutching. I change IAC. Plugs and wireds. Nothing worked. Today the high idle became constant. It was a metal bubble flex tube near the IAC unit that goes to the exhaust stuff down behind the motor. It apparently was cracked cause today it broke causing the constant high idle sound like a vacumn. We blocked it off with a stick to get the idle back down to 900 rpm instead of 3-4000 rpm took we can get to auto zone for high temp hose per Chevy dealer. I hope this helps someone cause it was fustrating and costly.

i would tell the dealer u want a second opion bescause my 2004 cavlier idles sometimes high it it turned out to be the rpm were wrong