My 04 SO cummins 5 speed has started missing at high rpms, around 2000 and higher, especially climbing hills. I have also noticed this under moderate to heavy acceleration as I shift through the gears. It won't do this is 1st, 2nd, or 3rd gear but really noticeable in 4th and 5th.
I have 52,000 miles on this truck and I tow a 6000# trailer.
The lift pump went bad and was replaced at 23,000 miles. This truck has no mods, it is running stock. Dealer put a new air filter and fuel filter in at last maintenance schedule, but has made no improvement.
Does anyone have any ideas what this could be? I love the truck other than this.
Thanks guys, this is my first diesel truck!

 

is it an HO motor? it maybe having an injector faliure

 

No, it is the SO (235) motor.

 

Sounds like pluged fuel filter to me.

 

my first move would be to hit with some POWER SERVICE DIESEL CLEAN avail. at wal-mart,gray bottle,and see if this helps,also if you have run bio-diesel lately change the fuel filter one more time,BIO cleans out the fuel sys. to the point that the fuel filter gets plugged, good luck and i hope this helps.

 

Injectors.

 

Could it be the lift pump? The higher the gear the more load and the more fuel required. My truck will do it once in a while in 5th or 6th gear. I have the EZ/Juice stack and the more I ask for fuel the more hesitation I get. Only in the higher gears though. I know I'm pushing the lift pump capabilities and will get a FASS setup soon.

Wouldn't injectors cause problems at idle and in other areas? Just my .02.

 

I just had the fuel filter replaced. Truck ran great for a day or so, but now it is back to hesitation. I will try another fuel filter, and also run the diesel cleaner through it. I am kinda thinking the lift pump is the culprit though. Would'nt this throw a code or something, if the lift pump is going bad?

 

Putting cleaner in there will clean everything , anything cleaned on tank side of filter gets stoped at the filter. Try another filter. You might better run slower ( less rpm ) let cleaner do its job for a while then change filter again.

 

When my lift pump causes hesitation, it doesn't throw a code. I do back out of the throttle when it happens though. It could be a host of other things as well though.

There were a couple of threads on guys who have had the lift pump relocated in the tank on their 04.5's under warranty. I'll try to find the posts so you can compare symptoms.

http://wwww.dodge-diesel.org/dev/sho...ight=lift+pump

I would PM dieseljunkie and ask him what his symptoms were. Good luck.