I have a 2019 FWD automatic Buick Encore with the 1.4L Ecotec engine. It's at about 80k miles. In recent weeks, I have noticed an occasional issue where the car is chugging/lurching (seemingly misfiring?). However, there are specific circumstances that correlate with almost every occurrence. It almost always happens when accelerating uphill, either on an uphill on-ramp to a highway or just some steeper hills on local roads (generally 45+ mph). Additionally, the vast majority of instances happen when the air conditioning is on.
There have been no check engine lights and no stored or pending DTCs when I use OB2 scanner. Initially, I suspected that the spark plugs may be the issue, so I checked them out. 2 of them were slightly more worn than the others and 1 had a bit of oil on just the threaded part of the plug. Replaced all the plugs with ACDelco 41-121's. While I noticed a marginal improved in acceleration at lower speeds, the occasional misfire/lurch/chugging is still happening. I also checked the MAF sensor and throttle body to make sure they weren't dirty, and they were fine. Visually inspected the ignition coil pack for cracking/burns and didn't see any. PCV valve (common Ecotec issue) also seems good.
The turbocharger was replaced (under warranty luckily) 2 years ago when I encountered a power loss issue. That issue was significantly more frequent and harsher on acceleration.
I'm kinda running out of ideas. I figured I'd post here before going to mechanic. My worry is that the issue is so infrequent with no DTCs that going to a mechanic may be wasted money.
Anyone encounter something similar to this? My only other guess is that the ignition coil is bad, even though there's no visual signs. Since there's no DTCs, I can't pinpoint any cylinders. And even if there were DTCs, it's a rail-style coil pack so I can't swap coils to see if the problem follows.
Maybe it's just normal? I know it's not a powerful engine and maybe the load of accelerating uphill, combined with AC on, is just too much?
Thanks in advance for any responses/advise!