I was chasing a 507 code for a while. Found out it was the pcv grommet. Replaced with a AC Delco pcv valve and grommet from the dealership. No more 507 code for a week and smooth running.

 

^^Yeah...save your pennies. I couldn't believe how much those Delco wires are.

 

The PCM uses the IAC to create a vacuum leak which increases idle speed. When the IAC retracts, it opens a passage in the throttle body that allows a portion of inlet air to bypass the throttle plate, this is what causes the idle rpm to increase. If the throttle stop screw is backed out all the way, and the throttle plate is fully closed, and it still idles too high, either the IAC is not fully extending to seal off the bypass, or there's a vacuum leak. Those are the only two things that will increase the idle speed.

 

If my $$$$ allows, I will grab a throttle body from a junk yard, i found one called speedway in illinois, and i know they have the same year same equipped vehicle. for now, it runs good, the idle bothers me, and the lack of a cat on there, not sure yet. have not welded it back into place yet.