Have an 03 that smokes black at idle and has a knock to it got injector balance checked and they were with in 3 point between all 8 but when you shut number 4 injectors off smoke goes away and runs smooth. So pulled even bank apart and there is engine oil in number 4 injector line is this a cracked injector or something else and all 8 injectors were replaced a year and a half ago

 

Your name states you have a 6.2. you posted in a Duramax forum, and then its says you have a Cummins......

Anyways.. Bad Injector

 

I started of with a 6.2 that I put a turbo on that I sold and then I bought a cummins and I work on my friends duramax

 

That makes more sense! LOL

 

LOL..

 

^^ That was my thought as well!