I have a 2004 with 200k miles on it and recently I have noticed a sudden decrease in fuel economy and acceleration is poor at times. I replaced injectors at 196k and my FICM is normal voltage (46-48v). I really don't know what coul be causing this. I took it in for a service and they saw the EGR valve was bad so they cleaned it and we unplugged it an i started running stanadyne formula in my fuel and I began getting 23mpg highway. Well that lasted about 2 weeks and then my mpgs slowly began decreasing and my turbo psi was increasing. Just last night I filled up and calculated my mileage and I got 15.1 mpg. Well that's too low and I need to do something. At first when all this was happening I took it to a transmission shop and they said they heard something internal and sounded serious. I later heard this shop gets sued quite often so I took it to 2 other shops and they said everything was normal. And that's what made me think it was engine related but I don't know what it could be.

My symptoms are a very loud idle, loss of fuel economy, and higher turbo boost with a sputtering sound. Also no exhaust smell in the cab which is good.

Anyone know what could be causing this?

 

cracked up pipe? stuck vgt? brakes dragging?

 

Very loud idle can be a bad injector, even if new, and or a weak FICM, just because it seems to test right doesn't mean it isn't weak. you probably have higher boost because your faulty EGR valve was fixed, they bleed off boost when they are bad.

 

Here is a video I uploaded to YouTube of my truck idling. Read the description too and maybe this is why it's louder?

 

Did you check fuel pressure? A weak pump will starve your injectors. . It will run poorly with very low fuel pressure. Check soon as low fuel pressure can damage injectors.