For awhile now I have experienced intermittent serious hanging throttle. I'm talking about when shifting the revs stay where they are or even go higher after hitting the clutch. At first it didn't happen very often but lately occured more frequently as well as surging while at steady throttle. I tested the IAC by applying 12 volts on the pins and heard the click like you are supposed to. I checked it with a multimeter and got a reading within the normal range so I ruled out the IAC. I changed my plugs and wire for the surging but that didn't help. I checked for a vacuum leak but found none. Finally, I thought I might as well pull the IAC and try cleaning it since that didn't cost anything except a little time, a cheap gasket and some carb cleaner. When I first pulled it, it really did not look all that dirty. I expected it to be full of crud. I've driven the car for two days now and no more serious hanging throttle or surging. The car is smooth and throttle response is back!
When I picked up the new gasket before the cleaning (66 cents and not necessary if you are careful) the Ford counterguy told me carb cleaner would melt a plastic part inside and destroy the IAC. He had to agree that cleaning it first made sense because it could work and if not, you would have to replace it anyway, melted or not.
I've already added cleaning the MAF to my regular maintenance routine. I'll now add cleaning the IAC, at the first sign of idle problems.
