My 2010 Nissan Altima Coup V6 (manual trans) has been having idle problems for several years. My mechanic says he thinks the problem is with the throttle body being dirty. He says cleaning it is an expensive project not worth doing. Almost every time I come to a stop in moderate temps (35°-60°) it idles around 1200-1400 rpms until I tap the gas peddle. BUT this seems to be weather dependent. At temps below freezing it idles around 600 rpms. At summer temps it almost stalls at a stop then catches itself and idles normal. It now has over 110K miles but this started around 30K.
Watch Scotty’s video on how to make your car run better with a little spray cleaner.
Also, check & clean your Idle Air Control valve (IAC).
Oh, and find a new mechanic.