2004 Duramax smoke like a frieght train, and on power
 

Ihad a problem with my 04 diesel smoking everytime i stop. I would get out and prime the fuel at the housing because i thought that i had air in the fuel it would start skipping when i sit at the light in traffic, it would not have any power to take off, it just smoked like a train. I met this shade tree mechanic ,and asked him about replacing my injectors. He told me that an injector will be either be good, or bad no in between. He said my fuel system was containmenated. He told me to get a gallon of lucas it would free up the water,and trash in my tank. I did what he said. I still had the problem so I took all of the hoses a loose clean them, and i went to order a new fuel filter housing. I got a little upset, and put everything back on the motor. Fired it up it sounded dead no power, no turbo, white smoke. So i took everything back off of the motor. Checked the turbo, it was ok. So i put everything back on the motor again, not knowing that i had forgot to hook the mass airflow sensor back up. iI fired it up drove it about 4 miles it ran very good. I had a check engine light. I went straight to Autozone had them check the light it said m.a.s. so i hooked the sensor up my truck ran like crap. I disconnected it and the truck is running very very good with the m.a.s. unconnected. I'm going to replace the mass airflow sensor. I can do burnout again. Try this and tell me want you think if you are having problems.

I may be wrong on this but a buddy of mine had the same problem with his 05 Duramax. I wanna say the dealer told him it was carbon built up? Sorry if I was no help! Good luck!:tu:

If you have an oiled airfilter then the MAF sensor may have been dirty, which will cause smoke and poor performance, have you checked your air filter lately? it may be dirty as well

black smoke means you have too much fuel and not enough air, intake is where i would look first in that case