when i start it up it idles high, about 2000 RPM then goes down then up then down and so on. any ideas. can this effect how the transmission shifts?

 

sounds like dirty IACV idle air control valve,,car been sitting a while or old gas in it?
thats located inside the throttle body
remove TB from engine and flip over- remove round cover and remove rod- clean air slit and chamber with carb cleaner
Buy new iacv cover gasket and TB to manifold gasket at dealer
best to remove intake manifold and tb- clean egr system as thats cloggin up by 75kmiles

both will affect trans- it likes to be low rpm when going into gear