Manager Forum

We have a 2003 Duramax that is smoking at idle. Most that we have encountered previously have been really bad by the time they show up here, but this one is not bad enough yet to be as obvious of a diagnosis. 3 things jumped out at me in the data. MAF 37 gm/sec @ idle and air filter very dirty, Main Fuel 3.4 mm3 @ idle, and Balance rate on #8 injector was 3.5 mm3. (#1 was between 2.5 and 3.2, and # was -2.5). If the positive balance rate means that the computer is adding fuel, then wouldn't the injector that is causing the smoke be the one that is too far negative, like -2.5 The truck runs great all of the time, it just smokes at idle, a little worse when warm. We didn't have the truck for long, but I can get it back in if I have a plan of attack. Any help would be greatly appreciated.

First thing i would do is clean the intake of all the crapolla. This will take a while no doubt. Look at the temp reading for the pcm. Check for any air leaks that would force rich. Make sure the oil isn't contaminated, i've seen this on occasion. If an injector is leaking this is something that will cause an issue and possibly a solvent in the fuel will clear it out. Possibly a turbo issue. The gray smoke sounds like a build up of moisture and possibly a breather issue. If the build up of crapolla is severe you may resolve the fault bit not know it because the smoke will continue for an abnormally long time. A restricted air filter will cause the turbo to suck through the seals and cause smoke. If you mat it to the rev limiter does it increase the amount of smoke? I'm going with there are no codes. I use my tech 2 on issues like this since it will be much, much more sensitive. There could be something keeping the throttle open just a bit knocking the idle control out of whack. Good luck.