VNL Fuel mileage reduction and power loss!

Hello I have a 2013 VNL730 with approx 640,000 miles. Its been rough finding a mechanic that fully understands the D13 engines even at a Volvo it is hit or miss. So I have decided to try this forum for the first time to see if I can get some answers. I have completed all new injectors and cups, new EGR and New DPF Sensor and Harness to try and resolve the issue. Also completed PM and regular service.

Problem
I am getting an issue that comes and goe's not changed by being loaded or not. this is causing a reduction in fuel mileage by 2mpg and power. Turbo seems to be providing correct boost as this does not change when the issue is present. I get a rough idle when sitting still and turbo when set on clean idle will fluctuate from 1.5 to 1.7 rpm's for a few min before settling to the normal of 0.5-0.7 RPms during the clean idle setting. Keep in mind this does not happen all the time it is inconsistent but definitly feeling the difference when the problem is active while driving. Also no Codes are active! could this be some sensor going bad?

I have thought maybe bad fuel so I treated the fuel and replaced the fuel filter which did have some algae present but has been cleaned. Also no algae in the tanks these have been inspected.

If anyone has had the same issue and been able to fix please let me know.

Thanks agian.

 

Thank u for the reply some good advice, we did check for boost leaks which volvo fixed about 2k miles ago, as for regens nothing abnormal but I will look into whether the EGR is getting stuck open and have them do a cylander balancing test as well.

Will let u know what the result is. One thing I forgot to mention was I do have a very slow injector harness leak would this cause these symptoms?

 

Ok thank you for your input will keep you posted how things turn out

 

sure that would be great atleast something to try as a temporary fix as the leak is very slow anyways