Time Sensitive: Desperate for Help with 2013 Buick Encore

Hopefully moving across the country Monday and can keep the car at the dealer until Monday. Have researched as much as I can with this and am hoping someone can help.

Backstory: In June, my car was leaking coolant and, long story short, needed the entire turbocharger replaced. The check engine light was still on, and I was told that was an issue with the light, not the car. Well, I got back and drove it 10 hours up to Mass (I’m in Ohio) in July, and it started having issues.

Issues: When starting the car after a long period of time or after it rains (this is something I’ve noticed), the idle will be rough. Rough like shaking back and forth for about a minute rough. Along with this will sometimes come an inability to accelerate the car. If I wait, this will usually pass. It has also come with a burning hair smell that sometimes smells a little more like gasoline. Once, I was parked on a Hill and I had the same issue and “Hill Start Assist” came on and made it hard to switch out, a couple days later this came back on when I was not on a hill. (Also possibly worth noting that all of the issues started up after I was lightly rear ended, but I think these are unconnected).

Tried to Fix It: Took it into the dealer in Mass, dealer diagnosed it with a bad catalytic converter and replaced it. Did pressure tests, etc. after the new converter was in, everything checks out and the check engine light is now off.

Same Issues But New: When I came back from Mass, thinking everything was fixed, I had the same rough idle and no acceleration; then when I was on the highway, I had three separate instances of the car not accelerating past 50mph.

Now: Car is being driven by dealership and other than a rough idle in the morning, they can’t find anything wrong. They said they will check on whatever I ask for. My biggest worry (which is something that was mentioned by dealer in Mass) is that I have a cracked head gasket that isn’t failing pressure tests because it is running fine when warm but not running properly when shifting from cold to hot (this would explain the rain issue and it sitting for a while).

If anyone has any suggestions, please please let me know. I really don’t want to have to sell this car, etc. but they don’t seem to believe anything is wrong.

I am not sure if this matches your issues, but the 1.4L engine in your car had big issues with the valve cover and integrated PCV valve that can cause some odd symptoms. GM had either a warranty extension or recall for the issue.

Is that due to the engine not being sealed and unmetered outside oxygen containing air is being brought in to the air intake, which acts like a vacuum leak?

If it runs rough but then gets better after a short time I would check the mass air flow sensor, then ensure that all the spark plugs are in good working order. Then check for vacuum leaks.

I really have no idea. Take it to a good mechanic who won’t just replace the catalytic converter and not fix the problem that caused the converter to get ruined in the first place.

No experience w/your car or engine, but rough idle problems often caused by vacuum system leak, pcv system, or egr problems. All three manifest most at idle. So those are the places to focus. Shops will sometimes spray starter spray (ether), if they find a place the engine starts to run better, good chance of small vacuum leak in that area. Replacing pcv valve usually pretty inexpensive, so worth a try. The way I test the egr on my truck and Corolla both, apply vacuum to the vacuum input w/hand-held vacuum pump, should stall engine at idle.

Turbo problems could be a cause too. Ask shop if there’s a way to disable any turbo action at idle, see if that has any effect.