Chrysler Aspen idling bounce/ surge

[mcdlnwright]

Hey Guys i have a 2007 Chrysler aspen 4x2
I have been very pleased with the truck until now.
I have been having a issue with the idle. It will normally idle around 5rpm. but lately it will "bounce" between 5 and 10 and you can feel it going up and down. it will happen for a while and then sometimes stall out. it will start right back without a issue most times a very small amount of times it will take a few tries to start.

I took it to my mechanic and he said he couldnt find the problem. This is my wife and kids daily truck so i need to get this fixed asap

Not sure if this has anything to do with anything but I get the check engine issue a very few times its always the gas cap is loose error. My wife said she puts it on right but it never happens when I put gas in.