Volvo: Need help trying to figure out whats wrong with my volvo, cat converter, nuetral

Question
I have a 1990 volvo no turbo. Just replaced the starter now my car is dying alot. Dies when I stop if I dont put it in nuetral and sometimes still dies. I thinks its leaking oil. Sometimes when driving wont get up and go. RPMs when stopped is bouncing and will drop to 0. Can u please help me?

Answer
Alena,
Wiring to the idle speed motor unplugged, bad idle motor, carboned up throttle housing. Clean off the engine and then run the engine with the proper amount of oil and watch to see where the leak is coming from. Test fuel pressure and see if there is a loss of pressure when the power is low. Has the fuel system been cleaned lately and the filter replaced? Check for a tune up. Has the cat converter been tested to see if it is starting to clog up?