Low powered LLY

[bdpuller]

Wondering if someone could provide direction on where to look next on my '05 to find the power it used to have. Pickup has 165k currently, but problem started gradually showing up about 2 years ago. I've had Bully Dog on level 1 for majority of truck life and was always very well pleased with power--it would run like the wind with heavy loads on tandem gooseneck. Power slowly dropped off to the point where it won't pull your hat out of the creek, especially below 2000 rpm. Acted like the fuel filter was majorly plugged up-but wasn't. My GM diesel tech can't find anything out of spec-injectors, fuel pressure, turbo, etc-and no service light or codes have been set. Did change mass airflow sensor, but didn't help. Tried taking Bully Dog off(back to stock) and running top level, which actually is worse than original stock performance. Very little difference was noticed between levels. At the top level, no smoke is visible at launch (WOT). Pump and injectors are original and otherwise runs fine. I'm wondering if the fuel rail pressure sending unit might be giving false readings and changing performance w/o setting codes? Any help would be greatly appreciated. Thanks in advance.

[DmaxMaverick]

Welcome aboard!

Most likely suspect is the catalytic converter. Not uncommon for running a power box/programmer for a long period. They won't usually set a code. Secondly, the EGR valve, for the same reason. It could be sooted, and preventing complete closure.

[bdpuller]

Cat has been removed long ago when I installed a free flow exhaust. Forgot to mention that I opened and cleaned EGR valve, but nothing wrong.

[bdpuller]

Tried changing fuel rail pressure sender out with another known good unit and got no change. I also just installed an EGR delete kit (wish I had done long ago) and surprisingly not set a code or light yet. Need some help!!!:confused::confused:

[ToddMeister]

Maybe a problem with the turbo/vanes, if the truck won't make boost the ECM will not give the motor more fuel. Do you have a boost gauge?

Or someone with a scanner can monitor engine sensors while driving?

Also check the injector balance rates.

[bdpuller]

Turbo and vanes functioned correctly when last checked. Even at idle, you could hear the fluctuating of vanes now and then. We did drive and scan and nothing showed to be out of place. Could ECM just be whacked??