Why does a diesel run rough ( not fueling evenly )at certian rpm's? Mine has been at 1000 to 1300 and now it is up to 1650 rpm.
Why does an engine (BUCK) at these rpm's as if it wants to shut down?
It has bucked at 2200 rpm ( and that was under load and on a hill )how come??? as if you are turning a transistor on and off with electronics shutting off one cylinder?
Does anyone have osociliscope reading for this and the associated info or can I fax my osoc info to them? I shouldn't have to spend my time tring to fix this!!!!!!!!!
99 24V

 

It really sounds like it's a computer problem. Either a sensor is bad and throwing evrything else off, like Chrismas tree lights, or its the engine control itself. A good computer technician will take a search to find. Just because it's a dodge dealer or cummins shop does'nt gaurantee good work. Personnal recomendations are the best way to find a good tech. You may have to travel out of town to get to one.

 

dont mean to state the obvious but have you checked your air filter and turbo boots? if your getting some boost id check the air cleaner see if its blocked. a diesel needs air and fuel so if you got fuel try the air

 

A bad boost pressure sensor (or any sensor for that matter) can and will fail and not throw a fault code. This is due to the sensor failing within the normal voltage threshold. This fools the ECM into thinking that nothing is wrong and will not throw a high or low voltage code. Have any of these techs monitored boost pressure? If you have a boost gauge and it is showing boost, it does not mean that the sensor is sending a good voltage reading (boost reading) to the ECM. Have someone monitor the boost pressure off of the databus.

 

They have changed to air and fuel filters many times and nothing has changed outher making my wallet a lot lighter and have changed the MAPS 4 times and that hasn't helped eitherand they all measure within 400 ohms of each other so suspect that they are fine. This is definently an electronics problem for I have the osocilloscope signals to prove it but no one can will read them to say what is wrong.
Heres one I have 1 volt Peak to Peak on the fuel shutoff this to me is very low and the rest of the signal is about 1/2 a volt positive and negitive. To me this is too low and is shutting off the pump signal and is part of the problem. Ive got the scope readings.

Had to learn about the insert key and how to disable it!!!!!!!!!
Now what have I forgot to mention? Are we able to look back and read the threads??? How do we do this.????

 

I get very little boost until into 4 th gear then it starts at 1600 rpm.

 

I won't embarrass (or maybe I should ) I have been to Vancouver area, most of BC, Edmonton and Calgary Must say that one on the techs their was quite interested and listened to me and put the DRB on and found no codes I left him my phone number and haven't heard from him. And of coarse cummins is of no help. been there and done that. You can guess the places that I have been to. Have even talked to Bosch back east many times Germany and to Poland. That was very interesting that was. So if you can help offically of un please do!!!!

 

Never, I am no expert on this, but if you are experiencing no boost until 1600 rpm, could you have ingested something in your air cleaner that is blocking airflow through your intercooler?? Next thing, could the boot that feeds your intercooler have the infamous "fender rubbed hole in it" which would negate any pressure from building up from the turbo until you get up to higher RPM's. I know that these items have been discussed in here before and some of the same problems you are experiencing were observed. I know you are getting wacked out oscilloscope readings, but they may be due to sensors reacting to the lack of pressurized air.

Good luck,

Gary

 

But the idle and off-idle readings are ???? bad. But guess should pressure test this some time when thed temp allows and make sure that it is good. As well this has been since new so there shouldn't have been rube through at that point??? Thanks more for me to ponder.

 

does the wastegate actuator move free? if it were seized in the open position, it might cause the low power problem...?

 

Northwest Cummins has some pretty good tech. , I would take it to them and have them put it on the dyno , and hook up with insite , then they can check what your readings are and also find out what user fueling state, if it was me , I would pressure check your whole CAC system , waste gate actuator and not just seeing if it moves , but pressurize the actuator and make sure it does not leak, at the most you will have two hours billable and will have a much clearer picture of what is happening , why they hooked up a box to the pump seems funny to me , the only reason we hook up a box to the vp44 is when the engine is not running and making sure it is not the pump.