04 Grand Prix GT, automatic. Yesterday I cleaned out the throttle body and MAF to get rid of the hit or miss starting problem. When I took the air filter off, I noticed that the bottom of the box was not sealed and the air filter was not seated in the box right. Big thanks to the idiot at Penzoil in Hartford if you are reading this!
So now I put it all back together and it runs and starts flawlessly. So, there has been a CEL on for quite some time now. PO455 evap emissions leak (large). Could this have been due to the airbox? I got the code cleared now, so I have to wait and see if it comes back and I will post if it does. Also, the gas cap light always comes back, even after a new gas cap. That light is also cleared now.
Any other known problems due to this code that you can think of? I searched and found anything from fuel pressure regulators, to the first 02 sensor. Thanks.
