Guys i was a member here back the day. Long forgot my user name password, ect. I have this 2005 dodge, auto trans, 2500 4x4. Heavy truck, has flatbed, replacement bumper, 315-70r17 tires.
I cut and hauled firewood to get through college when the truck was new, lots of 25,000lb loads up the texas caprock. I always thought this truck was verypower full. That gets me to today. For the last 6 years i have only put 6,000 miles total on it. It gets an oil change once a year. When i drive it its pulling my 20' gooseneck with a couple sandrails on it.
The other day i got a good load of scrap iron, gross weigh everything was 22,000lb and i had to haul into a 30mph wind. Anyway it gutted my pickup, it wouldn't let me set my cruise on 65, it was constantly downshifting. My first though was to blame the big tires, but now that i think of it, i hauled many heavier loads uphill and never noticed it being so gutless.

Just bought a 5th wheel and dont want to gut my pickup. How can I diagnose if i have an issue like a bad injector? The auto trans is original, its not strong anymore....
Pickup had a complete fuel system in 2007 at 80,000 miles (changed a fuel filter in the dark, had rusty diesel, big mistake) it has 120,000 now. The shop in clyde texas supposably put stage1 injectors in (shop manager was very shady, so cant verify). Also running smarty s06 on #3 and BHAF.
I have noticed that the pickup smokes light brown going down the hwy with a mild load. Doesnt seem to roll coal like it used to when i hammer down though. (Its actually pretty disapointing, i remember it smoking alot in the past) After sitting for a month i get a little white smoke at start up and it occasionally pops out the exhaust . (Only the first warm up after sitting) seems my egt runs higher than they used to. Also seems my fuel mileage is down. Used to get 17-18 with no trailer, but seems im down to 15-16 now, 12 with an empty trailer 8-10 loaded heavy no wind.
Any help would be appreciated guys. I do plan to go back to a 265-285 tire and rebuild and beef up the trans in the future.

 

Sounds like it could be an injector issue, but I'd start with the cheap stuff first. Do you have a FP or RP gauge? I'd change the filter out, just to be safe and pour some silver power service to it.

The fuel pressure and rail pressure gauge will help rule out a bad lift pump or CP3 issues.

Do you have any codes?

 

I would look heavy at the fuel system...the way you describe the long period of non use you are a prime suspect to have algae grow in your fuel tank especially if the tank is not full when you park it.

Change the fuel filter like madhat suggested and cut open the old one, look for black slimy stuff, it will plug up everything!

When fuel sits a long time in a tank especially one that is only partially filled, it heats and cools and moisture forms on the inside of the tank ending up in the fuel and creating a ripe environment for algae.

There are products that you can put in the fuel to help keep it from going bad on you when you park it for long periods like that.

 

The 315's aren't helping either.

 

Thanks for the replied guys. No lights on, but I havent scanned it.
I have a dummy light at the banjo fitting into the pump, so i know its getting fed properly.

The other day when i filled up i put a heavy dose of power service. Burning that diesel today. I have a semi tractor on my trailer today. (- the 6-71 im keeping) seems to be pulling excellent now. Im was running 65 on flat ground 1800rpm. No wind, 60 degrees trans was 165 steady. Water 210, oil psi just over 40, 21psi boost, 1050 egt.

Maybe the wind was worse than i gave it credit for the otherday. Will definetly be going back to a normal tire size though.

 

One other note. I still have a "smoke switch" wired in from when i ran quadzilla xzt. It rolls coal like normal when i flip it and hit the throttle.

 

What is this smoke switch you speak of?

 

The smoke switch. Tells the computer its at full boost so it fuels like crazy. Originally it was made to help spool the turbo when drag racing i think. But you just flip it and blip the throttle and smoke pours out.