LMM with delete package. All was fine for several weeks then started smoking at idle. Now smokes bad - like blacks out the parking lot bad. Seems ok going down the road but fuel milage sucks. I suspected injector but all ballance & closers look good. No codes. Starts great & runs great. Any ideas?

What programmer are you using?

Any other mods? Need more info on your truck.

If it is smoking at idle, it is getting too much fuel, which would point to an injector failure IMO, like a cracked tip leaking down. With EFI Live, you can turn one injector at a time off and see if one is failing.

With the deletes, I'd go see Mark at Danville Performance.

Using custom software written & installed by a friend. Had factory tune put back in. Flashed 3 times to make sure of complete overwrite. Still smokes just as bad. Talking to many differant techs it seems like it would be hard to start if leaking injector due to high rail pressure required to start. This thing starts at the touch of the key.

Black smoke? What does it smell like? Raw fuel like a cold weather start? Or, garden variety black smoke?

A lot of common rail injectors in Cummins have gone down to high rail pressure from custom tunes. Don't know specifically if you can tweak the rail pressure on a Duramax.

If you hook it up to EFI Live, you can turn each cyclinder off and see if one is causing the smoke. That would be my first step.

Smells like raw fuel. Its overfueling at idle something awful just don't know why. I think I'll take it to another guy who can do cyl cut out. My scanner can't do it. My budy with the GM tool says everything looks normal on his. Hoping for just a sensor.

Might overfuel and/or change timing if it thinks it is really cold out; bad IAT? There are two IAT sensors.

Let us know what what you find out. Hope it is cheap!

Sounds like it's trying to regen.

Sounds like it's trying to regen.


Thats exactly what I thoght & hoped at first so a simple software change would fix it but GM tool says it is not in regen mode. IAT reads correct on scanner.