i need help with my 90 jetta

i'm not too good with cars, so i figured id ask for some help ...i went to park my 90 jetta today, and when i placed the car in park, the rpms went way up (almost to 3000). any ideas as to what could be wrong? i have no idea.. thanks!

I've never run into this before, but if your transmission isn't working properly, the engine may have been pushing hard and placing it in park allowed it to spin. If you haven't changed your transmission fluid in the last 20,000 miles you probably should.