I have just replaced the Transmission Control Solenoid on my 2003 Neon SXT, and put everything back together. Started up the car, it immediately started running at 4K RPM's and not dropping. I replaced the Idle Air Control Valve sensor and restarted the car, it started smoothly at a normal idle. I test-drove the car, to test out the transmission, that was fixed. However, while I was filling air in my tires, the oil light came on. As I began driving home, the car started to act like the throttle was stuck, and the brakes were very hard to push down, when slowing the car down. I've searched the forum, and vacuum leaks kept surfacing. Can anyone help me on this issue??

 

Well, did you check for vacuum leaks yet?