i have a honda civic hx 2001 and recently i have had some problem with it, it started to shaking and rpm drops very low at idle and stall when press the gas even sometimes it just turn off, but there is no codes being shown, it runs like crap i don't know what i can do to fix this problem, recently i have cleaned the throttle body, new iac valve, new map sensor, new motor mounts, new spark plugs, new pcv valve, even a new transmission but the problem is still there. please help!!