Help! 2003 Duramax All Stock Is Smoking Bad At Idle And Driving, L

red87chevy · December 5, 2009

I am working on a friends 2003 Chevy 3500 4x4 crew cab dually that he bought new and it now has 90K on it. The truck is 100% stock. Apparently about 15,000 miles ago the truck began losing power and smoking excessively. The truck smokes blue smoke at idle and it smells like unburnt fuel. There are no codes active or stored and the truck is using no oil and is not "making" oil either (fuel dilution from injector bleed down) Any suggestions on where i can start. From what he is telling me, he brought it to 2 gm dealers and neither one found anything. I am looking for any known issues or obvious directions to head with troubleshooting this problem.

Thanks in advance.

Silverado4x4 · December 11, 2009

I am working on a friends 2003 Chevy 3500 4x4 crew cab dually that he bought new and it now has 90K on it. The truck is 100% stock. Apparently about 15,000 miles ago the truck began losing power and smoking excessively. The truck smokes blue smoke at idle and it smells like unburnt fuel. There are no codes active or stored and the truck is using no oil and is not "making" oil either (fuel dilution from injector bleed down) Any suggestions on where i can start. From what he is telling me, he brought it to 2 gm dealers and neither one found anything. I am looking for any known issues or obvious directions to head with troubleshooting this problem.
Thanks in advance.

Injectors need replaced, sometimes you wont see fuel in the oil. That is a LB7 motor and to replace the injectors is a big job as the heads need to be pulled. LB7 motors are known for injectors thats why they extended the warranty on them but I cant remember how long it was extended it may be to 100,000 miles. They came out in 2004 with the LLY motor about mid year and called it the 2004.5 and they had injector issues also but not nearly as bad, early 2004 trucks still had the LB7 motor.

kundog · January 7, 2010

Two questions...

1. Blue smoke is indicative of oil consumption (bad rings, turbo seals, valve guides) Are you sure it is blue and not white?

2. Has anyone replaced the fuel/water separator? Almost sounds like water in the fuel...excessive smoke, no power, and such...get a sample of fuel from the tank and put it in a clear glass or plastic jar...water will sit in the bottom.

If both of these are inconclusive, then I would look into the fuel delivery system, but I am sure you have tried the above, for grins have it hooked to a scanner and see what the sensors are doing as well...bad connections can throw values off...but not enough to throw a code.

red87chevy · January 31, 2010

Thanks for the help all. Just wanted to update this thread with my findings. I found out that the injectors had been replaced under warranty in 2006 and only had 25,000 miles on them since. After hooking it up to the gm scanner at a dealer and standing over the tech performing the injector test, 3 injectors failed. All injectors were replaced and truck now runs fine. Kinda sad that GM would not warranty there replacement injectors being that they knew they had a problem and there "updated" injectors only lasted 25k before crapping out.

Silverado4x4 · February 1, 2010

Its a kinda hit and miss deal, my buddy has the LB7 motor with over 160,000 miles on the factory injectors and never replaced, the injectors are made by Bosch.