Vacuum issue maybe?
I have a 2013 jgc 4x4 laredo and on cold starts the idle will act a little weird.. If I just turn it on and gently tap the accelerator , the idle will shoot up to about 3500 rpm and stay there and sometimes climbs for like 10 seconds before slowly coming down. I notice on upshifts as well ... For example I'm driving around 10 mph in second gear and accelerate abruptly for it to downshift, it'll downshift but hang at the high rpms for a couple of seconds before up shifting back to second . I can let off at this point , and it'll still hang for a bit.
I've had a replaced head gasket done recently