Subaru Problems? Ask a Mechanic for Answers ASAP
My name is ***** ***** I am a professional here at Just Answer. I noticed that your question had not received a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.
Since there is an electrical fault with the rough idle and is most affected when cold or in the cold this sounds like a possible electrical connection fault causing this here.Inspect the battery cables for any issues and if any issues are found this will need corrected.If the cables are corroded they will need cleaned and if they are damaged they will need replaced.If these are or were already checked and found o.k. let me know so we can continue.
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Can you tell me how the electronics are acting up on your vehicle here,what they are doing when this occurs?
If the belt was slipping around the alternator this can cause this type of fault here and the cold will affect the belt from gripping on the alternator properly.I have had to replace the belt before when it was worn slipping like this here.If you applied belt dressing and this helped the issue here this may be the case and the belt may need replaced to correct this fault.I would check and see if this is the cause here as well as make sure the alternator connections are clean and tight.
I would have the alternator tested as well as even though it is putting out voltage the amperage from it may be weak when cold causing this here and it may need replaced.
It sounds like an electrical fault here.I would have the amperage tested from the alternator and maybe check for any loose or damaged battery cables at the battery or alternator and starter.Check for any loose or damaged wiring for this fault.
This is a tough one for me to answer fully myself.I will have to open your question up for others here to see if anyone else can assist further.I hope you can get this resolved with ease.