Bought a used 2003 Chev 2500 HD, with D/A, and 46000 KM,(30000 miles) on it.Going down a fairly steep, slippery, winding road from a ski resort, in 4wdH, with the Tow/Haull mode ENGAGED. With the foot off the accelerator and the engine holding down the speed to 40-50 KM/H, or 30MPH, repeatedly when gently or abruptly pressing the accelerator on straight sections, a considerable amount of blue smoke blows from the exhaust, not just a puff, but for a considerable distance,before it cleared up.The engine had been properly warmed up, the ambient temp was about -10C or +15 F, and the altitude about 4500 Ft.As this is my first diesel, and not familiar with driveability of a D/A, had not noticed anything unusual in my first 100 miles of city and Hwy driving.What could be the problem, what tests could be performed to isolate the problem.Appreciate any constructive suggestions,as to further selftests or dealer tests required.The vehicle had been fresh prepped by the dealer with oilchange (15-40),fuel and airfilter changes,full tank of local fuel. 2003 Chev LT,CC,LB,lb7, stock, Vin checks out OK.

Diesels will smoke ,positive it was blue not a grayish haze? My truck will smoke blue (incomplete combustion) when I start my Max on cold mornings.

Keep an eye on oil consumption. If None then most likely it's fuel perhaps some bad fuel.

Mac

When coming off a ski hill the engine is still pretty cold and will cool down as you coast it down hill. To slow you down, the engine acts as an air pump and sucks (vacuum). Some off the holdback is from the restriction in the exhaust (turbo) but not as much as the variable vane setup on the LLY. The rpm is up, thus oil pressure is up. The throttle pedal is closed so fuel flow is low (unless you have leaking injectors,then you would notice dark smoke in town on acceleration). You could be sucking oil (blue smoke) (have to look close because off the coloured mirrors) (tilt the mirror down to see the exhaust pipe) through the cylinders (not broken in yet, not likely but possible), through the valve guides (worn out, cooked seals, but not too likely because of well drained heads), really cheap oil (compounds the previous problems), or sadly the most likely the turbo bearing seals are hard from shutting down the engine with the turbo hot. A simple way to check this is drive around town in T/H mode (light load, high oil pressure because of the rpm) and watch your exhaust for the blueish smoke on acceleration. This is not an immediate problem, just need to watch your oil. It will get worse over time and coat the inside of your intercooler and reduce its effeciency. Hope this helps you diagnose your own problem (can't really diagnos over the internet so take it all with a grain of salt). Good luck. I bought my truck at the dealer in town and nice bunch of guys,great coffee, but they aren't the brightest stars in the sky when it comes to solving a problem. They will probably start with "could be bad fuel" so they don't have to get into another Duramax. Geo.