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Discussion Starter · #1 ·
I replaced all my injectors on my 2004.5 5.9L HO 325HP because the old ones were showing signs they need to be replaced. Immediately after I got it back the mileage started to decrease and it continued to fall until it was at 13 mpg and it was at 18mpg. The injectors were replaced with Bosch OEM injectors. The shop that replaced them claim that it just happens to Cummings sometimes. Anything I can do or is the shop right.
 

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any new extra smoke, white or black with the new injectors?

any performance enhancement toys on the engine?

Bosch rebuilts or brand new? how do you know? boxes with part number?
new bodies and new nozzles?

need
cold and hot idle 2000 rpm cruise and WOT rail pressure
boost, engine coolant temp measurements/readings.

I'd find another shop if those are brand new fresh from the factory Bosch injectors and nozzles.
5 mpg drop with the same driver, something is not right.

some of the mileage drop could be explained by summer #2 last fall with higher mpg on your old injectors and many places are still on winter mix.
Texas should now be back on summer mix pure #2 now.
 

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Discussion Starter · #3 · (Edited)
They said they were new injectors. There is black smoke when I accelerate quickly. The shop read me the right part number from there invoice. But I'm not sure that's what they put in there because they won't open it up and actually look at the injector to verify PN. I added a edge mileage max tuner after the mileage fell. And no response. I've been told maybe the truck needs to be reflashed.
 

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what boost you seeing on WOT, should see at least 35 psi.
if not, then a boost leak. happens when mechanics are crawling around on top of an engine. things get hit and knocked loose.

boost leak kills mpg and acceleration

they refuse to even check their work quality?
 

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Discussion Starter · #5 ·
I assume WOT is the turbo. I'm not sure what the boost is or even how to check it. How can I check the boost psi. I had the ECU reflashed today and now I get a lot of black smoke when I really hammer on it. But It looks like the mileage may be recovering. Not sure yet. Gotta put some more miles on it.
 

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I had an issue with power and mileage after someone worked on my truck. I had someone tell me I probably had a boost leak and to check the intercooler. Turned out that the bolts on the hot side of the intercooler were loose. I tightened up and my mileage is back up. I also replaced the air filter at the same time, but I do thing it helped.
 
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