Rough Idle 2018 STI WRX HELP!!

OscMor

New member
A couple months ago I started to notice a rough idle when the car comes to a complete stop. (The car has 30,000 miles)The rpms shoot up a bit and drop back down to normal. It only happens when the car is warmed up, comes to a stop, and when I turn the steering wheel when I am also at a stop. The car also feels like it wants to stall out at times when it rough idles but doesn't. I was under warranty and I took it to two Subaru dealerships but both still can’t figure out the issue. They replaced the MAF sensor, MAP sensor, oil control valve and the problem still persists. The car has not thrown any engine codes. The car is stock with no performance mods. Has anyone ever experienced this or knows anything that can help out. I figured it could have been a vacuum leak but wouldn’t the dealership look for that too? I have a video of what the car is doing I just dont know how to upload.
 

magnetite2020sti

New member
I have a 2020 with 280 miles on it. At a stop just idling it will vacillate the rpms a tad if I move the wheel. It does not however, dip low enough to stall the car. But, it will go into a rump rump idle for a few seconds then back to smoother idle. Unless you have a dirty air filter I would say it is normal.
 

Alin

On a quest of STi erudition!
@OscMor

My 2004 STi does that too if I'm stopped and turn the wheel. Actually, any belt driven, hydraulic power steering will do this. It's due to the engine compensating power to the steering pump so you can turn your wheels without much effort while stationary.

Although, the part where your cars nearly stalls doesn't sound correct. Maybe there's air in your power steering? Maybe your spark plugs are fowled? I'm only guessing, so you'd have to discern for yourself.
 
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