2007 LBZ Sluggish

[BigLar368]

I have only had my truck about 4 months. I have since put about 3000 miles on it so far. I have noticed as of late it has been a little sluggish and slow to accelerate when you lean on the throttle. I have also noticed a slight decrease in fuel mileage by about 2 mpg in town and highway. At first I thought it just might be that I was getting used to it. I had already changed the oil and filter but held off on the fuel filter cause it drove so well. I recieved my edge insight monitor today and hooked everything up an noticed the fuel rail pressure would not go much over 8000 under full acceleration. I then decided to change the fuel filter. After doing so the monitor showed the rail pressure to go as high as 26000 and it felt much stronger. I am certain a partially restricted fuel filter would cause the performace issues but would it also decrease the mpg? I feel kinda stupid asking these questions. I was a heavy equipment mech. for 12 years and much of the work was diesel however most all of the work was never prevenitive or performance and was only as needed. Any input would be great. Thanks

[Runaway_Dmax]

Yes a plugged fuel filter would cause the milege to drop. I see you are in south Texas so I guess you aren't experiencing any of our below 0 weather we have up here in the Frozen Tundra today. Otherwise I would of said fuel gelling. You changed the fuel filter, mileage will more than likely increase too.

[Mark Rinker]

I am suprised that it never set a code and limped. My 2006s will both set codes and limp when the fuel filters get restricted from ice forming.

[BigLar368]

Yeah, here in Southeast TX it never really gets that cold. I keep it in my new shop (that has no door yet) so it never really gets that cold. When I changed the fuel filter I noticed there was no markings or lettering so that may have been the original filter. It was white. Not really sure what the color of the factory original was. It has never set a code or limped. When I unscrewed the petcock plug on the plastic portion of the filter only a few drops of water dripped out. I do have a friend of mine with an 06 2wd LBZ with 40K miles who gets codes constantly for fuel related problems. It is running much better and on another good note both my BD exhaust manifold and 4 inch Magnaflow downpipe back exhaust. Next Friday I will take care of my factory exhaust restrictions. Again guys thanks for the replies.

[BigLar368]

Update on the mileage. Drove 130 miles round trip almost all highway to Lake Charles, LA to a Rv show. I only have the DIC to calculate mileage because I have the extra fuel tank so its hard to gauge. However on the last trip to Houston before the fuel filter the DIC was pretty accurate with my hand calcualtions. The Houston trip was at 65 MPH all the way and the best the DIC showed was 18. This recent trip today was the same 65 MPH all the way. Outside temp was 42, RPM was maintained average at 1675 and no headwind at all. When I get home it showed 19.1. I also noticed the acceleration to be more responsive. BD manifold and Manaflow will go on Friday weather permitting. Again guys thanks for the help.

[Kennedy]

On my first Dmax (2002) I changed the filter at around 3k and I too felt it picked up a bunch. Ever since, I've made it a point to change the first one early, or at least watch the restriction closely. I believe that the first one can get loaded more quickly due to dust contamination in the tank, lines, break in wear, etc.

For future reference and to potentially avoid a premature filter change, we have a very handy test gauge that all Dmaxers should have:


http://www.kennedydiesel.com/images/Dmax-fuel-filter-rest1.gif