I have a 2009 Pontiac G6 118k miles, I've had it for 3 weeks now. It has an exhaust leak behind the cat, and "EVPD weak vacuum test" on the scan tool failed. All other tests were ok. After I got it immediately it would burn a quarter tank every 25 miles or so, it also hesitates when i come to a stop, as if im still pushing the gas petal even though im not. A week ago I noticed white smoke coming from the exhaust (not a lot of it and it went away after about 45 seconds), so my immediate first thought was head gasket leak. I began to pull the spark plugs but when I pulled the first Ignition coil it was drenched in some kind of fluid, it looked like oil. The other three were dry. I dont understand if this is all one problem, or a combination of problems. Is my engine shot?
Please don’t double post, thanks.
The oil you're seeing could be from something as simple as a bad valve cover gasket. You can add UV dye to the oil and use a black light to trace where it's coming from. (Scotty has done videos showing how to do this.) White smoke that goes away quickly may just be from condensation. (Are you losing coolant?)
As far as the problem with poor gas mileage you really need to check live data to see what's going on - and be sure you don't have a gasoline leak somewhere causing you to lose fuel while driving.
You can use a test kit to check if exhaust gas is mixing with coolant due to a blown head gasket.
https://www.youtube.com/watch?v=v0U8Iyf0kk4
https://www.amazon.com/Block-Tester-BT-500-Combustion-Leak/dp/B06VVBSFTF
The white smoke for a few minutes after start up is condensate and normal. The oil on the coil pack is probably a leaking valve cover gasket. Without a scan for code numbers, it is difficult to say where to start. I suspect you have an EVAP solenoid failure but cannot confirm without scanned codes. Please supply same.
The white smoke appears again when I start driving. Could this indicate a head gasket leak, or does the smoke have to be constant if the head gasket is leaking?