It happens about half the time in the morning start-up mode only. I'd rather hear my 'ol lady nag than that awful sound. (1) I wanna know if it typifies a larger bearing clearance than normal. (2) If it is probably the last bearing to get pressured w/ lube. (3) If I'm losing some bearing material every time it happens. It sounds like one rod only. I use 10-30 dino. It wouldn't be so bad if I could idle at a lower rpm upon start-up. These IAC's seem to be overkill, I realize you can't have motors dying on people when the A/C is on, etc. but I get tired of the constant revving the IAC causes. I put a flat washer in the IAC hose for awhile to tone it down but got paranoid and took it out.