I think my wife's '12 GMC Acadia has a stuck open fuel injector for cylinder #3. I have already had issues with this cylinder misfiring and the dealership replaced all the plugs and the #3 coil. I reckon this may have contributed to that as it started failing, maybe not though. I am no mechanic but I have no more trust in others to do a good job. Also the internet exists now and its all here. I am wondering what would cause this? Should I check the wiring and get a test light out? I should also point out that I have already changed the fuel pump in the fuel tank. It is acting exactly the same as it did before that.
Update: It was and I fixed it. I am the mechanic now.