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Trucker750 · 05-05-2018, **(Subject: Dpf cleaned and mileage dropped 1 mpg )**

I have a 2012 cascadia with a cummins 11.9 400 hp it has 620k on it. The dpf filter was cleaned and mpg seemed fine, but then 250 miles down the road the outlet NOx sensor went out and was about 1500 miles of reduced mpg. From 6.2 to 5.8 mpg. The sensor was replaced, but instead of mileage going back up, it went down even more to 5.2. I'm losing 1 mpg now and dont know why... no codes, so I need someone who might know what's happened???

imalumberjack · 05-05-2018, **(Subject: Dpf cleaned and mileage dropped 1 mpg )**

(05-05-2018 )Trucker750 Wrote: I have a 2012 cascadia with a cummins 11.9 400 hp it has 620k on it. The dpf filter was cleaned and mpg seemed fine, but then 250 miles down the road the outlet NOx sensor went out and was about 1500 miles of reduced mpg. From 6.2 to 5.8 mpg. The sensor was replaced, but instead of mileage going back up, it went down even more to 5.2. I'm losing 1 mpg now and dont know why... no codes, so I need someone who might know what's happened???

Could be totally off base but just want to bring it to your attention, have you up dated the fuel pump plungers? I have a 13' Pete with 11.9 @425 and it ate the plungers and caused fairly severe engine damage .... only has 205,000 miles

hhow55 · 05-05-2018, **(Subject: Dpf cleaned and mileage dropped 1 mpg )**

When they cleaned the DPF , did they do a maintenance reset?

Trucker750 · 05-08-2018, **(Subject: Dpf cleaned and mileage dropped 1 mpg )**

(05-05-2018 )hhow55 Wrote: When they cleaned the DPF , did they do a maintenance reset?

When they first did the cleaning of dpf, and my mileage dropped, I called and asked about it. And they told me they forgot to reset the ash accumulator, so 1500 miles later I was able to get it back to them and they reset it, but it didnt help.

Trucker750 · 05-08-2018, **(Subject: Dpf cleaned and mileage dropped 1 mpg )**

(05-05-2018 )imalumberjack Wrote:
(05-05-2018 )Trucker750 Wrote: I have a 2012 cascadia with a cummins 11.9 400 hp it has 620k on it. The dpf filter was cleaned and mpg seemed fine, but then 250 miles down the road the outlet NOx sensor went out and was about 1500 miles of reduced mpg. From 6.2 to 5.8 mpg. The sensor was replaced, but instead of mileage going back up, it went down even more to 5.2. I'm losing 1 mpg now and dont know why... no codes, so I need someone who might know what's happened???
Could be totally off base but just want to bring it to your attention, have you up dated the fuel pump plungers? I have a 13' Pete with 11.9 @425 and it ate the plungers and caused fairly severe engine damage .... only has 205,000 miles

The fuel pump was replaced in early 2016 at 425000 miles. Not sure about plungers.

Rawze · 05-08-2018, **(Subject: Dpf cleaned and mileage dropped 1 mpg )**

There are a lot of causes for fuel mileage dropping. Simply cleaning the DPF properly is not one of them. Something else caused it. Perhaps they worked on something else or replaced a sensor with a defective one?. Maybe a leaky doser injector?

Trucker750 · 05-08-2018, **(Subject: Dpf cleaned and mileage dropped 1 mpg )**

(05-08-2018 )Rawze Wrote: There are a lot of causes for fuel mileage dropping. Simply cleaning the DPF properly is not one of them. Something else caused it. Perhaps they worked on something else or replaced a sensor with a defective one?. Maybe a leaky doser injector?

They swear up and down they didnt touch anything else except the dpf filter. I know it has been a fleet truck belonging to them since new, and while they have always kept good maintained I'm pretty sure they have never cleaned any of the egr or intake system. I'm planning to clean it all, but I dont want to until I'm sure that is the sole cause of the mileage loss. Is it possible that a clogged intake system could account for the instant drop of 1 mpg just because the dpf was cleaned? Maybe the egr valve is so clogged it can't open normally, and the change is exhaust backpressure is now requiring more or less flow that the clogs will allow, equaling lost mpg? All without throwing codes? I'm a mechanic as well as a driver, but the computer systems nowadays are new to me.

Trucker750 · 05-08-2018, **(Subject: Dpf cleaned and mileage dropped 1 mpg )**

(05-08-2018 )Trucker750 Wrote:
(05-08-2018 )Rawze Wrote: There are a lot of causes for fuel mileage dropping. Simply cleaning the DPF properly is not one of them. Something else caused it. Perhaps they worked on something else or replaced a sensor with a defective one?. Maybe a leaky doser injector?
They swear up and down they didnt touch anything else except the dpf filter. I know it has been a fleet truck belonging to them since new, and while they have always kept good maintained I'm pretty sure they have never cleaned any of the egr or intake system. I'm planning to clean it all, but I dont want to until I'm sure that is the sole cause of the mileage loss. Is it possible that a clogged intake system could account for the instant drop of 1 mpg just because the dpf was cleaned? Maybe the egr valve is so clogged it can't open normally, and the change is exhaust backpressure is now requiring more or less flow that the clogs will allow, equaling lost mpg? All without throwing codes? I'm a mechanic as well as a driver, but the computer systems nowadays are new to me.

Also, would a leaking dose injector be found by doing a leakdown test on fuel pressure, and also would it be zeroed in on by elevated temperatures in the def system sensors? I'd like to know if I can say positively its leaking by simply using insite software.

tree98 · 05-08-2018, **(Subject: Dpf cleaned and mileage dropped 1 mpg )**

(05-08-2018 )Trucker750 Wrote:
(05-08-2018 )Trucker750 Wrote:
(05-08-2018 )Rawze Wrote: There are a lot of causes for fuel mileage dropping. Simply cleaning the DPF properly is not one of them. Something else caused it. Perhaps they worked on something else or replaced a sensor with a defective one?. Maybe a leaky doser injector?
They swear up and down they didnt touch anything else except the dpf filter. I know it has been a fleet truck belonging to them since new, and while they have always kept good maintained I'm pretty sure they have never cleaned any of the egr or intake system. I'm planning to clean it all, but I dont want to until I'm sure that is the sole cause of the mileage loss. Is it possible that a clogged intake system could account for the instant drop of 1 mpg just because the dpf was cleaned? Maybe the egr valve is so clogged it can't open normally, and the change is exhaust backpressure is now requiring more or less flow that the clogs will allow, equaling lost mpg? All without throwing codes? I'm a mechanic as well as a driver, but the computer systems nowadays are new to me.
Also, would a leaking dose injector be found by doing a leakdown test on fuel pressure, and also would it be zeroed in on by elevated temperatures in the def system sensors? I'd like to know if I can say positively its leaking by simply using insite software.

It will end up being cheaper and better to unmandate your engine. Just sayin