LB7 bad fuel mileage high EGTs

[Nick 6.5]

So I have come to summons the gods. I’m in desperate need of help. My truck is a 2004 CCSB lb7 FED with 250k. Cold air intake 3” turbo mouth piece. Baton compressor wheel Boost increase valve and off the shelf edge tuner. I’m lifted on 35 nitto mud terrains. So the story goes I use to get 18-19 flat highway unloaded. I have for about 2 years. 20-21 with AT tires. 17-18 hilly/mountain highway and 14-16 towning dependomg on load. For the past few months my mileage has been steadily decreasing and my egts have been increasing. I now get 13.53mpg hand calculated per tank on flat highway unloaded. Freeway is 800-1000 egt amd 1200+ towing. Engine use to burn super clean no smoke but now I have a small black cloud or brown haze under hard acceleration. I’ve checked all the basics. Intercooler boots all looks good. No obvious tears or holes. Boost still hits 22psi easily. Pressure test kit on order. My injectors balance rates are all +\- 1.5 on the worst injector most are around +\- .01-.03. Idle is smooth no surging. I’ve cleaned the MAF but honestly have no idea what to look for on the tech 2 for the maf. My actual rail pressure is spot on with desired pressure. I’m not seeing any real blow by from the engine. I gotta dona compression test still. But With with the “oil cap blowby test” the oil cap doesn’t puff up at all. I was told by a shop my cp3 is failing and that’s why I’m getting low fuel and high egt. But don’t see how that’s possible if my actual amd desired rail pressure are spot on. I’m totally lost. Any ideas or help would be greatly appreciated!!!

 

[MrMarty51]

Welcome to the forum Nick.
I’m not much familiar with this newer stuff, about all I know is that more fuel, or, less air will cause the EGTs to rise and fuel mileage to drop off.
I dont know what this engine has for a turbo but that could be suspect, but, if the injectors are beginning to leak and throw a bad spray pattern, that would hurt the fuel mileage, raise the EGT and could possibly burn a hole in a piston, or pistons. Might try a infrared thermometer and see what the temps of the exhaust manifolds are at the heads, after a road run, like make a hard run and pull over quickly and get the temps shot.
I would suspect that if an injector or two or three or ….was dumping fuel it could possibly be running warmer on that cylinder.
But I might be wrong too. I do know that @WarWagon had a leaking injector and burned a hole in a piston.

 

[Rockabillyrat]

The LB7 was known for injector issues due to the design on the pintle. But that usually causes hazing at idle, and you didn't mention any issues with that. So that leads me to believe you have a turbo issue. The LB7 is a non VGT so they didn't have the unison ring issues the later Dmaxs had. But I've seen plenty of LB7 turbos fail. Inspect the wastegate linkage for play, as well as the turbo shaft.

 

[THEFERMANATOR]

Check your boost tube for rubs where it goes by the power steering pump. Are you monitoring rail pressure while driving? How is your air filter? Fuel filter? What is your fuel rate when your checking your balance rates?

 

[Nick 6.5]

Check your boost tube for rubs where it goes by the power steering pump. Are you monitoring rail pressure while driving? How is your air filter? Fuel filter? What is your fuel rate when your checking your balance rates?

I looked for the rub hole from the power steering lines and the boots and tubing. I’m going to do a leak down test this weekend. I’m hoping it’s a hole in the intercooler that I just can’t see or find.. The fuel filter I change every or every other oil change and I change my oil about every 6k miles. . Air filter is clean. Yes with the live data I watched fuel pressures desired and actual while a friend drove. They were right in check with each other. What is the fuel rate? Not sure about that one.

 

[MrMarty51]

At the DOT, they had expandable plugs for the intercoolers, a system with a pressure regulator and a 1/4 turn ball valve. Plug one end and air it up from the other end, close the valve and if they leaked down so much in a given amount of time then they needed replacing.
We sent in quite a few from the larger trucks. I didnt get to mess much with the small stuff so I cant comment on those.
Usually if they was bad air could be heard escaping from the cores or tanks.

 

[Nick 6.5]

So not sure if this is what you were talking about. But calculated fuel rate in park is between 7.2-8.1 and in Drive is 11.4-12.3 are those numbers within spec?