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White Smoke or Hazing Exhaust on LB7 Duramax

Texas Diesel Company has the factory GM computer in-house! This allows us to quickly and effectively diagnose your vehicle saving you both time and money. We are also able to provide in-house programming of all components & modules installed in your vehicle, no different than the Chevrolet/GMC dealership would. If you’re another local shop interested in having us re-program a module for you, please call (903) 292-0400

This issue presents itself very often on the Duramax LB7 diesels. If your exhaust has a sweet smell (similar to antifreeze), it’s more than likely a bad EGR cooler or a blown head gasket. If your exhaust burns your eyes and smells like that of un-burnt diesel you probably need a set of injectors. The first test to perform is an oil sample. Using a white paper towel take a drop of oil and place it on a clean part of the towel. If diesel is present in the oil, a tan/brown discoloration will migrate itself away from the oil drop in the center. If this is the case, you are best to replace all 8 injectors. Diesel in the oil can dilute the viscosity of the oil and cause bearing, lifter, and other catastrophic internal engine damage.

Using a scan tool you can sometimes identify which injector is hanging open. Although we don’t recommend just replacing one injector at a time, here is how you can diagnose your problem. With your scan tool navigate to your injector balance rates. This test will be performed in park and in neutral. Push the brake pedal to the floor and place the truck in drive and monitor balance rates for at least 30 seconds. Look to see if any of the balance rates are ± 6. Place the truck into neutral and monitor if any of the balance rates are ± 4.


Should your injectors fall out of this range they will need replacing. If you only see 1 injector with a balance rate outside of the specified range, you can use a injector block off tool to see if the hazing goes away. We recommend using the tool from accurate diesel. This tool set will also work on 2003-2017 Cummins 5.9L & 6.7L diesel engines! Install the cap in place of the injector line which you suspect is bad. If the truck stops hazing, or starts then you have determined which injector is causing your problems! It is ok to temporarily run your vehicle with this cap installed.

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