My fiance jumped his friend's car about 3 weeks ago which sent a spike through our electrical system. Long story short we replaced the battery and the fuel pump that day. We also ended up replacing the fuel pump relay. About a week ago the car started to act funny again. The car doesn't start unless you have the gas pedal completely to the floor and when it starts its really rough for the first minute or so but then smooths out. We replaced the upstream oxygen sensor hoping this would fix it and it has not. Now my car is still doing the rough start but now when you're driving and you come to a stop, it dies. Can someone please help me figure out what this might be?? It's a 2005 Impala 3.4L base with around 156k miles on it. I have never had any major issues until he jumped his friends car.

 

We have contemplated changing the EGR Valve and the idle air control valve but we just don't want to spend anymore money guessing.

 

Is the check engine light on? If it is get scanned and it will lead you in the right direction.