Intermittent Idle Issue

Ever since I had my steering pump replace last month, I've had an Intermittent Idle Issue (the 'I' cubed issue?). It is very unpredictable so far. I've had days were it happens all day long, day's where it will only happen once or twice, and I had a stretch of about a week where it didn't happen at all.

Basically what will happen is I stop at a traffic light, I sit for a few seconds and the idle will dip and surge between 400 rpm and 900 rpm. Usually after a dip, the motor will surge and try to settle. You can kinda see it in the video below (it was at night so the video is really dark). Sometimes it will do it for a few seconds and stop like in the video. Other times it will just keep going. Yesterday it was really bad. I even thought it might stall once or twice. This morning the idle seemed solid.

A couple of weeks ago, I was cleaning snow off the Escape as it idled and I heard something that sounded like very faint backfires. I jumped in the car and the idle was jumping slightly. I tried to open the hood and see if I could pinpoint the sound but it only lasted a few seconds.

I did some research and my initial thought was the IAC as that seems to be the problem with 90% of the idle issues. I took it to a mechanic in town and described what was happening. Of course when I took it in the idle was solid. :cuss: He felt because it kept surging the IAC was trying to do it's job and correct the idle. He felt it was probably something else but if it wasn't happening, he couldn't trouble shoot. The check engine light hasn't come on so the issue isn't throwing any codes.

I was wondering if anyone else might have some ideas...