So I bought a GTA the other day. When I went to get it, it started up no problem, idled great, and went 70 miles with no problems. But now its very loud and rough on the start. It takes like 4 seconds to turn over and when it does, its extremely rough. I have to give it some gas so it wont turn off. The idle is rough. it also smells. But as soon i hit 5 MPH, it runs like its brand new. No power loss and shifts great. I was thinking possibly the fuel injectors. HHEELP!!

 

try cleaning the idle air control valve.

 

IAC sounds possible. Also check to make sure there are no vacuum leaks, stuck EGR, dirty throttle plates etc. Check all that basic stuff first and keep us posted.