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Pop/miss At Certain Throttle Position


flyingf

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Im a newbie!! Frank from texas. 07 mega 4x4 dually 5.9 cummins, fresh rebuild, arson kit cp3, rebuilt stock sticks, new tank pump, frame mounted 2micron filter, new map sensors, 63/68/14mm turbo, hamilton 210/188 cam, 160# springs, built 48re, new tps, bullydog gt usually ran on performance to help spool. Pop/miss at 20% throttle. Has done this forever. Even b4 rebuild. Have replaced everything and done everything i can think off. I am missing something tho. I am a field tech for caterpillar and this cummins has me stumbed. Also egts run high. 1000-1400 at cruising speeds. Love my truck but getting to my witts end on this and dont know what else to do. Oh and put a new ecm and updated flash program from dodge to see if it made any diff. None. AND truck only and has always since i have had it 12 to 13 mpg on highway and 11 to 12 city mpg. 5000# load to houston, 8to 9 mpg. HELP PLEASE!!!

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Yes sir i did. I replaced them 8 months before i did the rebuild. Had them tested by a bosch auth shop in houston. I took them back where i bought and they sent them there. I wanted to have them tested since i was doing an out of frame rebuild with mods. My shop said they tested within spec to run them. Guess maybe i should have gotten a 2nd opinion.

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Ok, that pretty much eliminates them. Didn't I read somewhere that some trucks have had a harness chaffing issue down by the A/C compressor? I don't know why that came to mind, but I remember something about it...l have a great memory, just that it is kinda short.......

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Find a shop with a scan tool that can capture snap shots while it is happening..........................just like Cat VIMS can :wink:  and go from there.

Even if you have to go to a truck shop and get a tech to hook up to it with Cummins Insight program.

What are the fuel supply and rail pressures doing when it starts popping? Does it have an exhaust brake?

Edited by Wild and Free
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My cat truck shop said they cannot communicate since dodge writes the programs. Dont know if thats true but cummins southern plains in dallas told me the same thing. I hate stealerships!! Rail pressure and supply pressure holds steady through the event. I may have overlooked but i did examine the harness closely during the rebuild. Acts like air in the system but if so its going to have to be either cp3, fuel rail, crosstubes, or injectors. Everything else is new and verified not to be leaking or sucking air.

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My cat truck shop said they cannot communicate since dodge writes the programs. Dont know if thats true but cummins southern plains in dallas told me the same thing. I hate stealerships!! Rail pressure and supply pressure holds steady through the event. I may have overlooked but i did examine the harness closely during the rebuild. Acts like air in the system but if so its going to have to be either cp3, fuel rail, crosstubes, or injectors. Everything else is new and verified not to be leaking or sucking air.

 

 

And yet you work for one lol!

 

Find and auto shop or demo a snap-on reader with snap shot capability then.

Edited by Wild and Free
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Excuse me but i was talking more of auto stealerships not my holt cat. Heavy end compared to light duty are two totally different worlds but people some are just part of the masses. Although all are allowed the freedom of speech sometimes silence protects the masses from being thought of in a negative light. Thanks for all the great points and suggestions. All will be tried and reported back on.

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Sorry if I offended you, you are new here and don't know me yet.. :doh:

 

I have been a heavy diesel tech for 20 years and have worked at 2 dealerships myself and was a field tech working out of a service truck for about 7-8 of those years. I just pointed out the obvious, you said it not me. it is not the dealership that is the issue it is the people who work there that give them bad names. I have seen and known incompetent people at Cat dealerships as I have at Auto dealerships and visa versa I have seen the most talented techs at dealerships also. The problem with auto shops is that their work is based on flat rate and they get greedy and take short cuts and just throw parts at things as that is what fixes a majority of issues and when it comes to having to spend time on troubleshooting which cuts into the flat rate profit of the individual tech then they just turn a blind eye and say they can't fix it. But I have seen this attitude from a lot of heavy equipment techs as well, some schools teach basics and do not touch on troubleshooting This is where bigger Cat dealerships shine they have awesome training facilities. Our local Dealer Butler Cat has an awesome facility in Fargo ND which I have been lucky enough to have taken classes at myself through a deal the mine I work at hashed out with them.

I know 2 awesome techs at our local Dodge dealership and they will go out of their way to help me with strange issues like the one you are having, I have had a couple stumpers they helped me work out, we have gone for drives together as I could recreate the issue or point out a subtle issue they could not and we then narrowed things down from there, one needs to work with the dealership not drop it off and leave, sometimes this is the difference in getting something fixed or not, not all problems are clear cut. As a tech I have spent as much time riding with customers over the years trying to get a handle on issues as I have done self diagnosis.

 

I am not knocking you, anyone who has been around any of several diesel forums knows that I am just joking around a lot and don't let people get away with saying things in general when one should be looking in a mirror when doing so.

 

Take my advice serious but let what you see as insults go past. I am not out to insult anyone personally it just comes out that way as I am a blunt straight forward type of person with a different sense of humor, I tend to catch things most others don't, my wife hates that quality,I find it fun. :thumb1:

 

You don't know of anyone with a scanner you could borrow? Heck a lot of diesel techs I know or have worked with over the years have more automotive test equipment than a lot of auto shops have as a lot do sideline moonlighting work on the weekends or evenings / heavy work during the day and light automotive and miscellaneous work in the off hours.

Edited by Wild and Free
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Thanks guys. No harm no foul!! I was thinking on same line as both of you but i did have one shop w/efi live hook to it and he said everything looked normal. Fca is new and i even went to the length of putting a new stock in place of the modded one but no difference. This truck has been to different shops and all say they dont understand y and especially at just the 20% throttle mark. I do know that is where cummins fuel pressure demand is cut for supposedly better fuel mileage at cruising speeds. Also please note. I try to make mods compliment other mods. All has been documented manually. Mpg never seen an increase on any mod until cp3 was modded. Seen a 2.5 to 3 mpg for the better. Strange i know.

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