turned up idle didn't help
when I turn the ac on check engine lite coms on on 1990 BMW 525i
Possible that your charging system is wearing out. Need to have battery and alternator tested to be sure they are producing enough power. Get code read at a parts store and post the result on here.
lite goes off when you shut off ac so no stored code
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Bring vehicle to shop. Don't be dumb, dummy!!
I't wont be your shop. "ASSHOLE"