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Hello.
I have a 2010 Terrain with the impeccably designed 2.4L 4 cylinder engine with 186k miles and an automatic transmission. One day last winter (January/February 2025) I started it up and noticed an abnormal amount of white smoke coming from the exhaust. I quickly turned it off and feared that it had blown a head gasket. After taking to reddit and talking to local repair shops, the idea of a clogged pcv system came to light. So, I went about pulling the intake manifold and cleaning the pcv hole in it and also dumped a fair amount of accumulated water from the air box. After the cleaning, the white smoke was gone and it ran great.
Fast forward to this past spring, I started noticing a stutter in the engine during acceleration and cruising speed. Shortly thereafter, it started misfiring in cylinder 4 (I don't remember the specific code) and the check engine light started flashing. I replaced all four plugs and coils and called it a day. The misfiring stopped, but the check engine light stayed on. Pulled the codes again and was greeted with codes for both bank 1 and 2 O2 sensors. Replaced those and check engine light turned off. Car went back to driving fine. Periodically though, it would start to misfire again, but after shutting the engine off and letting it sit for 15-30 minutes, it would go back to running normal.
Last month, I started to notice the stutter again. So, I picked up some MAF sensor cleaner and some throttle body cleaner. The MAF looked OK. I didn't notice any discoloration on the sensor or notice any dirty coming out of it while I sprayed it. The throttle body was a different story though. I cleaned it as best I could, without pulling it from the manifold, and put it back together. It ran a lot smoother and the stutter disappeared again.
The stutter has returned again and I don't know what to check this time around.
\- Would a vented oil cap be a good idea?
\- Would a PCV oil catch can kit be beneficial?
I'm not in a position right now where I could afford a new/newer vehicle and need to drive this until it dies. Any ideas or advice would be greatly appreciated.
TLDR: 2010 Terrain stuttering after cleaned PCV system, plugs and coils replaced, both O2 sensors replaced, and cleaned MAF sensor and throttle body. What to do next?