I'm having a bit of trouble with my grandson's 2013 Cadillac ATS 3.6L all-wheel drive,automatic with 154K miles. While I've had some experience as a backyard mechanic and have rebuilt engines in the past, I'm not a certified mechanic, but I'm doing my best to resolve this issue. The car intermittently experiences a misfire about every minute and a half when I'm stopped at a light, although there are times when it runs smoothly without any misfires. The problem doesn't seem to occur when the vehicle is under load. There is no check engine lite on and there are no codes recorded in the scanner. I've already replaced the spark plugs, all six ignition coils, the air filter, and I've cleaned several sensors. I've been using an OBD-II scanner while driving, and when I detect a misfire, I capture a freeze-frame of the data. Unfortunately, I can't seem to identify the root cause of the issue. It could be related to fuel or ignition, and it’s quite frustrating. Do you happen to have an OBD-II chart that outlines normal ranges for comparison with the problematic readings? Additionally, what potential issues could lead to erratic readings? Any guidance you could provide would be greatly appreciated!