Confussed LMM

[Mpsoldier]

my 2008 lmm has simple stuff done my overall work truck egr delete 4" exhaust turbo back trans go efi live tune. ok before i installed the lift pump i was able to hit 18mpg easy now i cant hit 14mpg same tune same everything confused can someone explain this bc i am heading to Texas tomorrow night from ct and would love to get 18 rather than 14 lol and if anyone has a better mpg tune that they would like to share i will reply with feedback for you np. tune is a 500hp approx been on the truck sense new.:thumb:

 

[coker6303]

If all you changed was a lift pump, you need to make sure you don't have a fuel leak somewhere.

Is the MPG showing 14 in the DTC or hand calculated?

 

[Ne-max]

Do you know how much fuel pressure you have? I've been seeing a lot of air dogs being to high from factory

 

[Tank222]

Unplug it for your trip and see what you get.

 

[Mpsoldier]

i will no leaks first thing i checked and running 12psi 150gph pump just weird never seen it before tank 222 going to try that next also waiting to do back to back sence its going to be like 4 fill ups

 

[Ne-max]

I don't suggest just unplugging it. That's more Crap the cp3 has to suck fuel threw. Witch won't help. I personally don't think the ad is the issue.

 

[Mpsoldier]

ok going to change all filters today and see wut happens

 

[othrgrl]

What type of EGR delete do you have? I would be pressurising the charge air system and checking for boost leaks caused by your EGR delete. We've also been seeing LMMs and LBZs lately with the EGR valves stuck open and they get bad mileage from it.

 

[onedirtymax]

Dustin, how do you tell if its stuck open? I'm having the same issue.

 

[Mpsoldier]

just a delete plate will pressure test it after lunch.

 

[othrgrl]

Pressurize the charge air system the same way we would to check for boost leaks. You won't hear it like an external leak but it will bleed off pressure quickly and you can hear the air going into the EGR cooler.