2004 6.0 misfire

Hi,
I have a 2004 6.0 silverado that sets check engine lite (sometimes misfire#7 and sometimes multiple/cyl misfire-I have a cheap OBD11 scanner). When I clear codes they don't come back except at an idle (not while driving on hwy). Seems to be much worse after driven on hwy, idles pretty well when its cold (open loop) and not to bad even in closed loop if not real hot.Also seems to do pretty well when I put seafoam in the gas.

I have changed spark plugs (wow those iridium plugs are expensive) and plug wires.

Anyone have any ideas where I should start looking?

Thanks,

John

Hi,
I have a 2004 6.0 silverado that sets check engine lite (sometimes misfire#7 and sometimes multiple/cyl misfire-I have a cheap OBD11 scanner). When I clear codes they don't come back except at an idle (not while driving on hwy). Seems to be much worse after driven on hwy, idles pretty well when its cold (open loop) and not to bad even in closed loop if not real hot.Also seems to do pretty well when I put seafoam in the gas.

I have changed spark plugs (wow those iridium plugs are expensive) and plug wires.

Anyone have any ideas where I should start looking?

Thanks,

John

random misfires are usually a fuel pressure problem..
with a guage measure for around 60 psi at the intake test port...then shut down engine and see if it holds pressure..

this is a common failure , forums are overflowing with this ...a little effort on your part, you should quickly get all that is needed to repair/test for this..

The 6.0s do have problems with intake gaskets and this one thing to check also.They blow out,sucking in air and will cause a miss.Yes,the intake gaskets are made out of plastic.Spray carb cleaner near the intake gasket area and if you hear a change,intake gaskets are bad.Most parts stores stock the intake gaskets since this is a huge problem on the 4.8s,5.3s and 6.0s

okay, I'm feeling pretty dumb here, where is the fuel regulator? Looked on the fuel rails and haven't found it yet.

John

okay, I'm feeling pretty dumb here, where is the fuel regulator? Looked on the fuel rails and haven't found it yet.

John

the driverside of intake manifold mid point is the regulator...has a vac line going to it...

on passenger side mid point is the fuel pressure test point...
measure fuel pressure and on fuel regulator check that you don't have fuel in the vacuum line...if so replace the regulator..

no vacuum produces maximum pressure....