I have a 1994 900se 2.0L Turbo. While not in gear, my engine rpm will will dramatically rise. sometimes up to 5000 rpm. Most of the time, if i then tap the gas, the rpms will then go down to somewhat normal. but this is not always the case. I have replaced the throttle positioning sensor and have noticed no difference. The problem is most noticed while not in gear, however while in gear the engine also seems to be at higher rpms. I also have a small exhaust leak, however I am doubtful that it is the problem. Thank you in advance for any help or advice.

 

could be your accelerator cable is sticking or something like that.