i just replaced injectors and cross over tubes in my 2004 CR 5.9 Cummins with new ones. I torqued them to specs. i still have a slight puff of black smoke when slight acceleration from of idle. It disappears when put under power, but wether warm or cold still puffs slightly when accelerating from idle. According to my over head display mpg's went from 18-21 before injector replacement to 10-13 mpg after. i am not showing any white smoke, nor is there any miss or shutter in idle. i understand that new injectors have a break in period so my mpg's will get better with operation.

What concerns me is when its at idle I can watch the mpg drop at a constant decreasing rate below 6.0 mpg. Should the mpg not increase while idling and drop when under acceleration?

I have checked my oil. There does not appear to be any significant difference in the level. Could this be a faulty injector, leaking coss over tube, sensor, turbo, or am i just looking for issues that are not there?

 

Did you disconnect your battery when you swapped them? I know it defaults back to 15.5 mpg and with the break in period it could be a little rich for a while.

 

Yes I disconnected both. I know the injectors have a break in period so lower mpg is expected, but why is the mpg's so low and getting lower when idling at a stop light or parked and running. Shouldn't I get better gas mileage than when rpms are higher when driving?

 

MPG's drop when idling or at a light because you are making no forward movement, so the calc is missing the m = Miles, but the diesel is still being consumed at idle.

 

Am I missing something. At idle with the truck not moving, the mpg is zero. My math says that the average would decrease.

 

I know when I idle my DTE actually goes up for a period of time and then starts to decrease again but that's after idling for like 5-10 mins straight

 

Thanks guys! Makes sense!

 

those computers are pos. The only way to properly figure miles per gallon is fill your tank on a long drive and figure it manually.