Column shifter broke on my 2000 Ranger 4.0. I disconnected the negative battery post before working on it. I followed instructions on how the take apart the dash and steering column area to allow the column to be lowered enough to change out the column shifter. Replaced with new items. Carefully reinstalled the column and dash parts etc. Reattached the battery ground and started the ranger to test shifter out. Immediately it went up to a high idle of 2000 or so. Wouldn't slow down. Let it warm up thinking that might help. It did a little, dropped to around 1500 or so. First thing I did was unplug the IAC and rpms dropped to 700 or so. Engine idled fine. When I plugged it back in the ilde went back up to 1200 or so. Pulled the codes and they were PO420 and 1540.So I cleaned the IAC valve and it was dirty, reinstalled. Cleaned the MAF, Intake air temp probe, and removed the TSP and checked it and cleaned the PCV. Checked for vacuum leaks, none found. Cleaning the IAC helped some. Unhooked the battery for a while. Reconnected it. Reset codes and drove a few days. Still has the high idle 1200 or it eventually idles down to 700 or so. But only after the engine has warmed up. After reading and watching high idles fixes on internet and youtube. I bought and installed a new AIC, TSP, and PCV figuring they need replaced because they still are the factory ones. Pulled code sand was PO420 and 1540 again. Unhooked the battery while replacing parts. Started the ranger and it revved up to 2000 or better and wouldn't slow down until the engine warmed up. Unplug the IAC and quickly drops to a nice 700 rpms, plug it back in and it revved back up. How would replacing the column shifter possibly cause this idles issue? At a loss as to do. Any help will be appreciated!

 

IAC and TPS, Sorry on spelling.

 

Sorry again the correct code is 1504 not 1540. Just frustrated with the thing. Thanks