Originally Posted by Gorving3
My 2001 Wrangler 4.0 seems to shift unnecessarily rough/harsh from P to R or D also, but it just seems the engine idles faster than really necessary. When I purchased it new I asked the dealer if the idle speed could be slowed down a little like we did back in the good ole carbureter days if the idle was too fast. Was informed that stuff is all computer controlled and no adjustment is available.
Too fast of an idle is not normal but as the dealer said it is not adjustable. What can cause an abnormally high idle? A vacuum leak (even a small one), a bad TPS (throttle position sensor), or a dirty IAC (idle air controller).
A search for 'dirty IAC' and bad TPS should bring up a lot of threads for how to clean/replace them. A dirty IAC can be cleaned, it doesn't need replacement. A bad TPS must be replaced, it can't be cleaned.