Hi -
I was wondering if anyone else has experienced this. When I am going down a hill (pretty steep grade) and hit the accelerator, the engine seems to stutter and spit out pretty heavy greyish blue smoke. Otherwise, the truck drives fine - heavy acceleration and all. Going down the hill, I am usually going about 60, but this morning I tried it at a lower speed, and the same result.

Thanks for any clues!!

Mike

 

I can only reference this to gasoline engines that produce large amounts of intake vacuum under deceleration. Due to weak piston rings oil is allowed to be sucked by them under high vacuum situations. Worn valve guides/seals also can contribute under these situations........

But since we've got diesels and they produce little to no intake vacuum, I've no definite answer for you.

Cody

 

I would hazard a guess that you have a bad injector o-ring or other internal oil leak.

When you are coasting the injectors are not firing, but the high pressure oil pump is still pumping, so a long coast with a bad o-ring could possibly allow enough oil to pass into the combustion chamber that it would go up in smoke when the fuel started flowing again.

 

Good call.....That was my next idea.
Stupid o-rings

Cody

 

I just did a warmer run of the same hill to check to see if it acted the same after a day of running. Not near as much smoke, but now I hear a pop and see black smoke when I hit the accelerator hard going down the hill.. Any possible relation? When it pops, it feels like an engine miss.
Thx again!!

 

Heavy black smoke generally denotes too much fuel or a lack of air. You may have one if the boots on your "Y" manifold sitting on there cocked and the pop you hear could be boost escaping as the boot seperates from the manifold.

When I blow the intercooler boots off of my truck it makes a loud pop followed by the gutless feeling of a diesel without a turbo.