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Pete, Automotive Mechanic
Category: Medium and Heavy Trucks
Satisfied Customers: 27932
Experience:  Performed various automotive repairs on several light duty and medium duty vehicles over 15 years of service.
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I have a n14 cummins plus and it runs good until it warms up

Customer Question

I have a n14 cummins plus and it runs good until it warms up then I cant get over 55mph and as it runs longer the speed starts to get slower to the point it wont get over 45mph. I can turn it off let it set for about 30 to 45mi crank it back up and it runs good until it warms up again. it is not showing any codes what do you think could be the problem?
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Customer: replied 1 year ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Pete replied 1 year ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.My info is somewhat limited on your model here but I had seen no one else has responded and would like to see if I can help here.If at any time you feel that I cannot help with this please let me know.

I have seen on some models where the exhaust can start to restrict as the engine runs in some cases.On models that have the DPF filter this can start to restrict as it heats up and can cause this here and on models without this filter this may be an issue with a component like a catalytic converter causing this fault.I would have the exhaust system checked/tested to see if the fault can be pinpoint and from there repaired.

Since there are no codes I dont see this as a fuel issue but it would be a good idea to have the fuel system tested for any issues with the high pressure fuel pump or one or more injectors possibly at fault here.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

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