Just did a head gasket on a 230k mile 4.0L with an automatic trans in my sahara. It runs and idles fine in park and neutral, but the idle falls and stalls when pulling to a stop. It doesnt do it if left in neutral rather than drive when slowing to a stop. Im reading check and clean the throttle body, the IAC and if that doesnt fix the issue it may be computer related. Opinions? How to check everything?