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Heath, Technician
Category: Heavy Equipment
Satisfied Customers: 147
Experience:  Certified in detroit, caterpillar, mercedes and everything freightliner offers
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2004 cummins isx 400hp over 600000 mi on it, only drove it

Resolved Question:

2004 cummins isx 400hp over 600000 mi on it, only drove it bobtail and its like 5 mi a galon on average. hooked a trailer to it and it was bellow 4 mi a gallon. Took it to a cummins crosspoint in nashville tn, and they found bad #6 injector, replaced it and still same problem apparently did a "scuff" test afterwards and found all injectors failing the test (5% allowed it was showing 8%). Been to dyno test it is putting a 325hp to the ground. No faulty codes but its still like 4.7 to 5.3 a mile bobtail. I know some people with simmilar problems and their trucks are not pulling uphill as they should and i am afraid that that might be the case with this one too (it has not houled a load since i bought it a month ago). Have you ever heard of those problems on cummins isx engines? and what to do to fix it?
Submitted: 8 years ago.
Category: Heavy Equipment
Expert:  Heath replied 8 years ago.
Hello my name is XXXXX XXXXX i would enjoy helping you with your problem but first i need to know some infomation. Has your truck started smoking any and how did it pull under a load 1 month ago?
Customer: replied 8 years ago.
well i just bought it a month ago and did not pull any load with it.
While drivin it bobtail my friend observed some smoke when i change the gears, otherwise it dont smoke at all.
Customer: replied 8 years ago.
i had other friends with the same engines in their trucks test this one some of them think it does not have enugh power bobtail some of them said it is fine, but it is still using to much fuel while driving bobtail....
Expert:  Heath replied 8 years ago.

Ok thanks for the info.. On the isx we have alot of troubles with the egr valves, even tho they are not codeing on your ecm they could still be slightly closed due to carbon build up. This will cause your engine not to get the proper amount of air into your intake thus causing your engine to work harder to keep up and also cause black smoke to occur occastionly and when your engine is bogging down like at 1500rpm its not getting the best fuel mileage or power it can.. And also the injectors over time on these engines cause the same thing.. On these engine the injector get weak at a earlier time due to the egr process. But i would take off the egr vavle first and ck for exessive carbon build up.. That is your most likely cause since it has just started.. Also your truck should get better fuel milage under a load becaue of the designes of your engine.

Customer: replied 8 years ago.
yeah they also performed a scuff test in crosspoint cummins in nashville tn ant they have said that injectors faild it, it alows 5% and it returned 8%, but still it shold not be that much in fuelk consumption. I will accept your answer and i am going to try to take of egr to check for a build up.. The truck is going on the road tommorow and i will check if the fuel mileage gets better . Thank you
Expert:  Heath replied 8 years ago.

Thank you for the accept and let me know what happens.. If you need anything else just come back and see me...





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