I have a 2010 Acadia with 113000 miles on it. I had an issue with the gas cap not sealing, replaced gas cap then the next time I filled it up it wouldn't start ( never did that prior to replacing the cap) I took it in the shop (GMC dealership) they said it was the purge valve, replaced it for $250.00.. Drove it off the lot and three check engine light came back on..took it back..now it has 2 new fault codes that were not there when I picked it up...codes are P0008 & P0017.. These are generic codes that can be linked to timing issues... After being told it was going to cost over $3000 to fix I got a second opinion. The mechanic cleared out the codes and said if it was a timing issue I would have poor performance and rough idling... Which I knew and tried to tell the dealership but was blown off..the codes were cleared out and that lasted about 8 hours ( if it was timing issues they would've come back immediately) anyone have any suggestions as to what's going on or had similar issues?