I would've thought if I had a head gasket problem that neither would hold 100psi at all.

Am I overthinking this and go back to look at intake/fuel injectors?

 

Alright, I put everything back together including puling the fuel rail and cleaning the injectors.
Fired it back up, same sound.
I decided to look at misfires in HPtuners VCM scanner to see if there was anything noteworthy. 1 misfire on cylinders 7 and 8 over a few minute run, so that didn't tell me anything.
I did decide to go through shutting off injectors again.... noticed shutting off injector 1 made the noise either go away or lessen a significant amount.... so that's where i start tomorrow.

 

Anybody have guidanc on how to troubleshoot cylinder 1? I'm swapping coils and plug wires first, then plugs themselves.
Since shutting the injector off seems to quell the issue, seems like the injector turns on and off, and i cleaned them this weekend, so hoping that's not the issue.
I "think" the valvetrain is good since bumping the starter made the rockers go up and down smoothly, and the leakdown test on that cylinder was good.
So good leakdown test and good rocker movement, can i assume valvetrain is good?

I feel like i'm going in circles a bit and willing to take any help i can get

 

ok need some help from the experts.
Cylinder 1 has a misfire that's audible. When i shut off cylinder 1 injector in VCM scanner, it quiets down a LOT, but idle obviously starts to stumble around a bit.
The car runs ok, and i've been learning to tune with this, but given the hunting idle a little bit coupled with the noise, I definitely have an issue

Here's wehat I've done
I have pulled the injectors and cleaned them. I have put 42# injectors in and tested those this weekend (w/ different tune but sound was the same)
I have swapped coils, wires, plugs. I swapped the entire set of 4 coil packs in case there was any issue in the coil pack mini-harness.
No change to sound and fact that I can quiet it down when i shut off injector 1
At this point, I have to have an internal issue, right?
I did a leakdown test and it was fine so I'm trying to figure out where I should be going next.

Any help would be greatly appreciated. I really don't want to take it to someone, but am starting to hit the limits of my troubleshooting abilities.

thanks
Jim

 

OK, I'm about to ask an incredibly odd and potentially stupid question.
When you place a 6.0 (LQ4,LQ9 gen III) in place of an LS1, do you need to do a crank relearn?
I thought gen III to Gen III with what should be the same sensor, you should not need to do it, but now i'm reading up on all these Cylinder 1 misfires and the fact that I can put a LOT of timing in my car without knock, i'm starting to wonder

 

What is the history of the short block? Fresh build? Used?
If its a used motor that sat. Could be the rings sticking. I've seen that many times. Some ATF down the plug hole, crank it a couple times, then let it sit for while.

 

Do a relearn. It isn't going to hurt anything.

 

Any reason to actually do a relearn?

I've got about 500 miles on the motor this year; is there any chance it still has a sticky ring?

 

I've done over 50 LS Engine installs and never did a crank relearn on one of them. They all ran great, don't think that is the issue.

 

Thanks Merv... didn't think that would be it, but wanted to ask... this misfire is really bugging me