A while ago, my 01 Sable started to idle very rough and the car became shaky while idling. The engine hiccups every 30 to 60 minutes and each time it hiccups the RPM drops from 900 to 800. After I replaced plugs and wires, it went away for about 3 weeks and came back. I just replaced PCV and it does not seem to help. What is the typical RPM for DOHV? I did a search and it seems to me that the next thing I need to do is to clean IAC. Where is IAC on DOHV?