odd idle problem after running 55mph
 

had no idle and had to goose the gas pedal in neutral to keep motor going after slowing down after a 12 mile interstate trip. got to my destination, and after a cool down of 45 min, everything was back to normal. no CEL. ideas as to what happened?

2001 4 cylinder

Other then the no idle issue did the engine operate OK? No hesitation, miss, lack of power, etc?

Idle speed is controlled by the IAC valve. An internet search on "IAC" valve will generate hits on how it works.

If just an idle speed problem the valve could need cleaning.

Or the EGR valve might have stuck open. If open, the engine will want to quit at idle speeds.

car runs fine. I was thinking of cleaning IAC, but thought that was more for cold starts.
I will consider egr clean also.

If the engine runs OK but will not hold idle check IAC valve. The valve is used to control idle RPM engine hot or cold. You need not take the valve apart to clean it.

The internet has many post on cleaning the IAC valve.