Subaru Problems? Ask a Mechanic for Answers ASAP
Is the check engine light on or flashing when the engine is running?
Unplug the mass air flow sensor and see if there is any change. Sometimes these fail and don't set the light. When you unplug it, the light will come on, but try it, unplug it and then start the car and see if it will idle and run better. If it does, then the car needs a new maf. It's pretty common so let me know.
Please let me know if there is any more I can do to help you from here.
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Did you unplug it with the car running?You need to unplug it and then start the car. Sorry if I wasn't clear enough on that point.
How does the car run off idle? Is it drivable?
Could be the IAC, but could also be a vacuum leak. Will the car idle long enough for you to spray some carb cleaner around the intake manifold. If it will, you can spray the carb cleaner and see if the idle smooths out of speeds up. You could use the maf cleaner for this as well. Just don't see the IAC fail on these often and really don't want to guess about it. Also, some of these had EGR valves. Do you know if yours does? If it's sticking open it could be causing the issue at idle.
Let me know.