I just bought a 2011 Tahoe LT with 42,000 miles. Great car, runs well, but the idle seems rough, especially when in gear. Around 500 rpms or just below in gear and goes just above 500 rpms in Drive, but still somewhat rough. No Service Engine Light coming on. Is this common? I plan on taking to a dealer to look at but was curious on what it might be.

 

That idle should be at least 700 rpm.

 

Try throttle actuator position sensor. This is a variable resistor connected to the foot throttle cable and actuator mechanism.

 

Try throttle actuator position sensor. This is a variable resistor connected to the foot throttle cable and actuator mechanism.

 

First try cleaning the throttle body thoroughly.