Posting for a friend 04 6.0

[OR VietVet]

I should have asked earlier. How many miles on this engine?

Found this at a Silverado forum.

"I have seen several 6.0 trucks through my shop with higher rpm misses. Most of the time it needed a mass air flow sensor and a crank relearn to fix it. I have seen a few intake manifold gaskets leak too. There is an updated gasket out from GM.

I would start by spraying around the manifold when the engine is stone cold and then when it's hot. If your scanner shows live data, it's better to watch for a change in short term fuel trim while spraying. RPM isn't always a great indicator. If you don't have access to data, disconnect the IAC (if you have a throttle cable truck) prior to spraying

Ohm check the injectors too. Look for all of them to be within a few tenths of an ohm.

A crank relearn will need to be done with a factory capable scan tool"


Plus, like Dan said, no harm in getting a fuel pressure reading when you rev engine above 2000 rpm.

 

[01FormulaTA]

nope no problems prior to this issue. no real loss of power or bogging down aside from the missfires. the codes that are coming up are just multiple cylinder missfire code nothing else. as far as afm im finding nothing but conflicting information. arguably gm started afm in 04/05 but only introduced it in the v8s in 07. also nothing but conflicting information if the 6.0 ever even came with afm anyway. 6.2 yes but the 6.0 im finding yes and no. i cant really go look at his truck myself or i could get faster information. but yes as long as he keeps the rpms under 2k it runs great. even if he has the truck running and in park if he gives it enough gas to get above 2k soon as it hits that point missfires start getting posted with a multiple cylinder missfire code.

AFM was not in any Gen 3 LS motors. A 2004 2500 will have a Gen 3 LQ4 6.0, no LQ4 ever had AFM. Also, no GM 2500 has ever come with AFM. There are many different variations of the Gen 3/4 6.0, no Gen 3 engine has AFM, however some of the Gen 4 6.0s did have AFM and some did not.

Off the top of my head:

6.0 No AFM:
LQ4, LQ9, LS2, LY6, L96

6.0 w AFM:
L76, LFA, LZ1

As mentioned above sounds like a Vacuum Leak or Fuel Pressure issue

 

[drakon543]

AFM was not in any Gen 3 LS motors. A 2004 2500 will have a Gen 3 LQ4 6.0, no LQ4 ever had AFM. Also, no GM 2500 has ever come with AFM. There are many different variations of the Gen 3/4 6.0, no Gen 3 engine has AFM, however some of the Gen 4 6.0s did have AFM and some did not.

Off the top of my head:

6.0 No AFM:
LQ4, LQ9, LS2, LY6, L96

6.0 w AFM:
L76, LFA, LZ1

As mentioned above sounds like a Vacuum Leak or Fuel Pressure issue

that corresponds with the majority of the information i found. guy is a pretty good mechanic but he is more of an old school muscle car guy. said he did the intake gasket as a vacuum leak was something he had already considered. i tell him to recheck for vacuum leaks and to check his fuel pressure.

 

[drakon543]

as far as the injectors unless a whole bunch of injectors went bad i cant see it being injectors related. he was trying to narrow it down so he swapped injectors from the 2 worse cylinder missfires with the 2 best cylinders. but again he is having missfires across the board its just primarily showing misses on 1 and 6 and 2 others. all cylinders show missfires just 4 cylinders have noticeable more. so something that can effect the whole process seems to me more of a culprit. as stated vacuum leaks fuel pressure. he can do live data but its a more basic advanced scanner definitely not a tech 2 so a crank relearn isn't going to be a diy for him.