Already replaced 3 o2 sensors , 6 new bosch platinum +4, plugs, oil change and transmission change last month, running out of solutions.

Check the fuel pump.

Does it happen when it's cold or hot? If it's happening when the car is warm, then it's most likely your coolant temp. sensor. There are 2 sensors, one for the gauge and one which the ECU reads. Do a search on here, I know there are a few threads on this. I want to say the sensor closer to the block is the one the ECU uses.

Happens when it's cold out and when it has been sitting overnight.

Hummmm lets see... Tune up time? When's the last time you changed your air filter, and plugs? Also clean your throttle body, that seems to be a cure all for lots of things lately. You may have a lot of carbon and gunk built up around the throttle plate, therefore not letting enough air to get in, hance you run rich bla bla bla.. Black smoke! Give that a shot. It still could be a temp sensor issue.

How would i clean my throttle body, thu a mechanic or ???

God no. They will way overcharge for this one.

check out www.motorcate.ca for directions

SuDZ

Did it do it before you put the Bosch plugs in?

Yes before and after, just happened this morning, passed emissions testing in Mass. though. ]

Actually, that was a dig on Bosch plugs. A lot of people have had driveability problems with those - especially Maxima owners.

Anyway, a leaky injector is a distinct possibility. Don't know how mechanically inclined you are, but you could start with some injector cleaner to try to free it up. If that doesn't work you could throw a fuel pressure gauge on the rail and look for a pressure drop after the engine is shut off.

Other than that, it could be a bunch of different things unfortunately.