When i start my car it starts off at around 2k rpms, where it used to start at 1200 and then move down to the standard 700-800. Also, when its in Park and Neutral the revs go up and down between 1000-1500. It will slowly go down and when it hits 1000 it revs to 1500, without me touching the pedal at all. I put it back into drive and it instantly goes down to 900, which is still a bit high. Also when im cruising between about 20-30 mph the shifting hesistates between 3rd and 4th gear like the car cant make its mind up. Its an automatic btw.

What could possibly be wrong, im baffled. I changed the oil but that really didnt do anything. Thanks.

 

1. vacume leak
2. sensor failure
3. Idle control valve may need replacement or adjustment.