2001 Altima Bucking

Ok i just bought a used 2001 Nissan Altima with approx 91 000km on it.

it runs like a dream but as soon as you idle the engine revs go down to 1000 then suddenly drop and the car feels like it wants to stall. the car shakes vilontly.

so i went to a mechanic and he said that a cylinder was misfiring and that i should change the wires and spark plugs..... did that today and it fixed the problem a little

there is still shaking but not as bad

upon inspection of the sparkplugs i noticed that 2/4 had severe corrosion, and the other 2 had carbon deposits...

im thinking i have to adjust the gappage on the new plugs, does ne one know what the designated gappage is?

thanks

Sacha De Sousa