I'll start off apologizing for the long post. But this is starting to get me worried.

I've been trying to find out what's causing my mileage to go down. My last trip to MN was about 20ish mpg. Which wasn't to bad since I think that we were still on winter fuel at the time. But the problem I'm having is that I'm getting about 15-16mpg in my normal driving when I was getting about 18+ last year about this time. I'm assuming that we've been switch to summer blend (atleast by now).

I know that my idiot *********** will not be able to find anything. Last time I took it in for the turbo making a grinding noise when I had a load. I can move the compressor well to were it touchs the housing. I also told them that it felt like the truck had a slight surging with a lot (@2000+#). They said that they couldn't douplicate the noise & would not go off of the specs that I printed out for the tolerences for the turbo. Unloaded the turbo would see full boost. So they said the turbo was fine. They can put a load behind the truck even though they sell the Airstream trailers... Some BS about liability and because that can't load up the truck to douplicate the problem. I asked if they checked the injectors becuase of the surging. They said they didn't because they didn't detect any. [sorry about the rant!]

Well now I'm starting to get slightly harder starts and my fuel pressure seems to be dropping when the power in the truck is feeling a little lower 8-9psi vs 10-11psi. But then next time I start it up, starts right away & power feels good. Oil analysis didn't show any fuel in the oil or any abnormal wear at 15,000miles on the oil. (I'll be doing another sampling at another 7,500 miles). The turbo is still occasionally making a grinding noise with a load & occasionally I can hear a slight grinding at idle. But I'm still able to get boost up to 38-39# (that is even with the X2 on 100hp, 60hp setting does the same). I've noticed that the truck is sounding more dieselly sounding (started around 43,000miles). I also can hear in the exhaust what I think might sound like a slight miss. Rail pressure seems to be fine, but a little lower than what I remember than before I upgraded my Commander to be able to use the next X2. (Cruzing at 70mph rail pressure as about 18-19k now its 17-18k.)

I have no white smoke and no additional smoke cruzin'. I do have a little rougher idle than I remember when I first to got the truck 35,000 miles ago used.

I was hoping you all could give me some advice on what to look for. I'm hoping to have a little time this weekend. I was planning on doing the crayola trick on the exhaust manifold to see which cylinder is running hotter or colder than the other.

The other thing that I can think of duing is disconnect one of the leads to one injector at a time. I'm assuming that I to be listening for a different sound in the engine. But I've never done that before so a little advice would be greatly appreciated.

Also any other advice would be great!

Sorry again for the long post. I just wanted to make sure that I gave you as much info that I could think to help me narrow this down.

 

Getting fuel at the same place every time will help on checking the consitency of your mileage. Some places that don't sell a lot of fuel are just adding summer blend to the winter blend already in the tank in th ground. 2nd) Have another dealer check the turbo. I doubt it is your mileage concern, but if it is out of spec, it's only gonna get worse. If your not still under warranty, have a Cummins shop check it out, or a reputable erpair shop. 3rd) I would have the valves adjusted. That could be some of the "dieselly" noise you are noticing. 4th) Have a reputable shop check the injectors. It isn't a hard test, and not very time consuming if they know how to do it. DON'T play with the injector wires.......pretty high voltage, you could get shocked and you could damage the ecm if you short it out!

 

Vzdude thanks for the info.

I usually fill up at the same Flying J 99% of the time just for consistantly good fuel. I'll re-adjust my valves to see if that helps any. I did them about 30,000miles ago.

How often should I adjust them? I was figuring about every 50,000 or so.

I guess I'm going to have to find another dealership to take this to.