Volvo Repair: Fouled plugs, mass air flow sensor, air flow sensor

Question
I have a 1989 740. I am changing my spark plugs ones a week. There are black the car is getting bad gas mileages and a little smoke out the back.
I had the car in for a tune-up and he said he cleaned out the in take?. The troubles started a month after that and started down hill.  I would bring it back but I am at school in WV and the repair shop is in NJ.


Answer
well i would suggest that you have a  fault with your mass air flow sensor, or your fuel pressure regulator. both are easy to repair, but need to be tested. the maf, requires knowledge of automobiles, the regulator, only involves inspecting the vacuum line by the thermostat housing. if there is any fuel or liquid in that vacuum line, then the regulator has failed. and needs to be replaced.