2001 Windstar Sport SE: "Idle Surging"

My mechanic told me after my last oil change that he noticed that my vehicle is “idle surging,” and was surprised that the check engine light has not come on yet. After this information, I started to noticed that when my car is idling the RPM needle jumps in the 0.5-1.0 RPM range. When the check engine light comes on he told me to bring it in right away.

What could be the reason(s) for the idle surging? What could I look for before I wait for the check engine light to turn on?

There are many possible reasons for varying idle. The two most common ones are an air/vacuum leak and a faulty IAC (Idle Air Controller - Ford often calls them Idle Air Bypass Valves).
It’s strange that the “mechanic” is waiting for a check engine light to go after this problem. Whatever it is is likely to involve some troubleshooting, and it is unlikely that the check engine codes would lead him directly to the problem. Is this a real mechanic, or someone at some chain store, like iffy lube?

Thank you for the answer. It is a place for me to start.

I do not take my car to places such as Jiffy Lube. The shop that I take it too is called Best Brake now, but it used to be Brake Masters.

It took a little bit of work, but the mechanic at a Ford dealer figured it out. A hose that connected to the PCV Valve had a hole in it. Also, the EGR Ports needed to be cleaned.

The van’s “idle surge” is now absent.

Figured I would share the resolution with the rest of you.