ok...it only happens when the engine has been running for about 10min. my idle is around 900rpm and when i turn on the ac before 10min, it idles up fine, after around 10min when the engine is warm enough, it would be erratic, sometimes it would idle up and sometimes it would just stall....most of the time stall. what could be wrong? thanks...pls help

btw...my engine is ph12...