871 Horrible fuel milage

[Rockycoon75]

I have a 11 pete with a 485/1850 871 18 spd 3.55 rears getting horrible milage. I bought it about a month ago. It has 100k on a dealership overhaul. I did the egr tune up when I got it. New imap delta p and exhaust pressure sensor. Doser injector was previously replaced and was pretty clean. Truck isn't smoking at all and water temp is running between 180-190 oil temp 210-220. No codes no lights.
Over the last 2300 miles I'm getting 4.8. Half of the miles were empty
Doesn't seem to matter if I run 60 or 70 still sucking fuel. Power seems to be good.motors feels to run best smoothest between 1300-1650 under or over its feels a little rough almost like a miss. Usually holds 32 on manifold pressure. I have seen it pull 40+ several times and at times only pull 30. Not sure where to begin with it[/size]

[Brock]

(03-01-2017 )Rockycoon75 Wrote:  I have a 11 pete with a 485/1850 871 18 spd 3.55 rears getting horrible milage. I bought it about a month ago. It has 100k on a dealership overhaul. I did the egr tune up when I got it. New imap delta p and exhaust pressure sensor. Doser injector was previously replaced and was pretty clean. Truck isn't smoking at all and water temp is running between 180-190 oil temp 210-220. No codes no lights.
Over the last 2300 miles I'm getting 4.8. Half of the miles were empty
Doesn't seem to matter if I run 60 or 70 still sucking fuel. Power seems to be good.motors feels to run best smoothest between 1300-1650 under or over its feels a little rough almost like a miss. Usually holds 32 on manifold pressure. I have seen it pull 40+ several times and at times only pull 30. Not sure where to begin with it[/size]

What kind of weight are you hauling when your loaded? What area are you running?

[Mr Hagg]

Have you did a charge air leak test? Also over head maynot be set right. Along with cam timing and a few other things. How does truck pull? May do injector bubble test too..

[Rockycoon75]

Pulls good between 13-1650 . Checked all the cache boots and connections and couldn't find a leak. Will have to check cooler when I get home. Overhead should be done this weekend.

[Nilao]

If it's dropping boost I'd suspect a silent derate. Also 40 on the boost is too high.

[Rockycoon75]

I've been trying to watch the boost and back out of it when it goes up that high. Just never know when it's going to do it. May be normal 32-33 for several pulls then bam 40+

[Brock]

My boost is always just shy of 40 on hard pulls