Oh and breaking my heart....

210,580 miles. CEL light came on two weeks ago, no difference in performance until two days ago. rough idle on stop, sometimes smoke, blue or white, I cant tell becauase it NEVER does it when I can get out and actually look at it. Runs fine when foot is on gas. Cant take it to one of the free places to pull codes, car is too old. Found somewhere to do it for $70, but money is tight. Obviously no one here can diagnose, but maybe a little advice?
BTW - I know nothing of how to take anything apart or fix anything. I do know how to change tires, check oil and all fluids and I used to have to spray carb cleaner into my first car all the time. Other than that, difficult instructions, and big words, will be lost on me.


Also, I have only owned the car for 9 months, owned a '94 940 wagon before that that was totaled by a red light runner, that had 260k I have ALWAYS used premium gas until about a month ago, when having the condenser on this car replaced (this car has been a nightmare) the Volvo dealer and self proclaimed Volvo God told me I was wasting my money, so I started using Regular Unleaded.

help?

 

Also, when I first bought the car, there was this electrical buzzing noise I thought was the radio (which didnt work, had to put one in), but it turned out that it was the external fuel pump, and then something about the Regina system. But he did not really fully explain any of that and seem bothered that I asked.