2006 Silverado HD 6.0l

[Thomas.berry13]

Im trying to track a power issue i cant seem to find. My 2006 Silverado 2500HD 6.0l gas burner has multiple random misfires with no engine light/codes. It has terrible fuel mileage, lags in acceleration really bad, and seems like its being held down. Shop says at idle in park engine load is reading 26%. What would cause these issues? Ive Already changed: knock sensors and harness, plugs and wires, catalytic converters, o2 sensors, and few other odds and ends. Any ideas will help.

[davester]

check fuel pressure.  If the pressure is low, the ecm just tries to compensate by dumping in more fuel, which is wasted because the injectors don't spray properly w low pressure.

 

as well, check if any exhaust manifold bolts are broken off, or if there is an exhaust leak at the joint between the manifold and the exhaust pipe (as the exhaust can suck clean air in, fooling the O2 sensors, and again, causing the ecm to dump more fuel into the engine).

 

It's also possible the intake manifold is leaking, but you should have changed it when doing the knock sensors...

 

[Formulabruce]

You will need to check the air cleaner assembly and make sure its clean. Also need to remove the air intake and Clean the throttlebody and Throttle plate ( Both sides) . Use Throttlebody cleaner and a cloth towel, not paper. This area has to be super clean.

 Good luck!

[MORSNO]

I'd check the fuel pressure, when my fuel pump started dying on my old '01 it acted just like that.  There was enough pressure to idle and run without a load, but once I tried to take off faster or climb a hill it acted up.  The computer tries to dump more fuel, but it's just not there.