My van in the past few months have gotten worse with idling when first turning on. It revs up quite a bit like if I would be pressing on the gas. Also when I put it in drive, it stalls and feels rough to the point where it almost feels like it is going to cut off. Also if I don't let the car warm up it will occassionally shut off when driving. I am able to cut it right back on and drive. I have had a Code 0442 pop up in which I got serviced and that they replaces a vapor hose at the canister. It was ok for awhile but it the light is back. I'm not sure if this is related to the problem.

I was wondering if a coolant change would help. Any advice or suggestions would be helpful.

 

A coolant change should NOT have any effect.

High many miles on it? Spark plugs and wires serviced?

It might be a dirty throttle body and/or idle air control motor.

I had a '93 Dodge Spirit with the 3.0 Mitsu motor which developed a stalling when cold and being put into gear. Cleaning the inside of the throttle body (carb cleaner and a tooth brush with the engine off and opening the throttle plate) completely remove my stalling issue.

Since the idle speed does go up and then down, makes me believe the IAC does work.

Another source could be a vacuum leak at idle leaning the motor out to stall.