I have a 2000 cummins 3500 with 164,000 miles on the Odometer
I have had the fuel pump, fuel filter and Injector pump replaced
The problems:
Truck cuts out sporadically....like dies for a second then comes right back...does not matter if I am empty or towing 15,000 lbs (scared the crap out of me when towing)
Also and this is hard to explain....While at cruising speeds it feels like my truck is struggling for fuel or air....If I throttle it...it powers right out of it, I am thinking maybe my injectors are clogged?
Oh and my fuel mileage has gone to crap....was getting 19, then dropped to 13....I ran 2 bottle of Lucas injector cleaner through and made it back to 16 mpg...but have not run my dually since filling up 3 days ago, I am afraid to until I know what's going on
Any information on where to start or to look or anything would be greatly appreciated

 

First off check for any codes first, but it does sound like TPS going out.

 

I would be helpful if you knew what the running fuel pressures were first but until you can acquire that information, do you hear any vacuum/pressure noises coming from the fuel tank cap when you take it off?

 

No codes
Is there a way to test the throttle position sensor?

I was told if the tps is failing my truck wouldn't idle....but it idles great

 

No, none

 

Really its very difficult to diagnose some things without the aid of gauges. People think gauges are for aesthetics but actually they should be mandatory.

If you should choose to, you can probably rent a fuel pressure gauge at your local auto parts store. I know the big name parts stores do that around here and the gauge they rent here is pretty good quality. The fuel system on your truck has test ports via shrader valves which allow you to easily tap right in and test idle and running pressures.

 

well it wont hurt and yes there is a TPS(APPS) reset you can do. use the search function on here to find it.

Also the cheap free stuff I would do.
clean all grounds pos/neg on both batteries. check to ensure all main ECM/PCM connections are good.
fuel filter I know you said you have replaced and all of the other parts but when?
I know alot of folks that just changed within a couple of months and winter fuel crap etc. etc.

look up Timbo's APPS on google. this is the replacement that is 4000 times better and cheaper than an oem/MOPAy/chrysler APPS.
you can also go on u-tube and look up Cummins APPS and shows some video's of when they go bad.

But if you have someone close to you swap out your apps for theirs if you think it is.

but I had a simular issue but on week 2 of the same issues it did give me codes and it ended up being my ECM was toast.

 

Problem has been solved
Took it up to Wentland Diesel in Milton Freewater, Oregon

Dually had 2 problems

First was that 3 intake gaskets were completely gone...There for poor fuel mileage

Second was the accelerator position sensor was failing...that's why I was feeling the slight surges

Good news was that my injectors were in perfect shape...they pulled them, cleaned them, tested the spray pattern, replaced the O-rings and adjusted them....
Thank you all for taking the time to give me starting places

I am not a mechanic, don't know much at all about diesels. ..but have been driving my truck enough to know when something just doesn't feel right

 

Glad you got it worked out.