What would cause a 2003 dodge ram engine to rev up while driving. It woll also stall Iif you put it in gear and mot push down on the gas

OK, I know I hear loads about the rev limiter, and having replaced only to have to spend more on tune ups, filters, breathers, etc, etc only to find that the problem is still there and that there were other simple typical problems overlooked that could be causing these symptoms. So you should know that these "other" things could be causing a variety of other "non" issues, some as simple as the distributor cap working it's way loose. Check that (as well as the spark plug wires) and make sure they are firmly seated and the cap is locked down tight (This has resolved this problem the last three times I've been asked to look into this). Second, these same issues are what you should expect from a dirty throttle bottle, remove the large air hose and clean the inside of the throttle body, making sure there is no gummy varnish holding the butterfly gates opened or closed. I like to use baby wipes as they contain no harmful chemicals and contaminants, one or two usually allow you to wipe the entire surface area clean. If after doing these things, the problem still exists, I would investigate replacing the IAC (Idle Air Control) valve. these are very simple and affordable things you should do to fix the problem, with no need to go much further.