**SOLVED: Coil ground wires behind the power steering pump had corrosion under the sheathing. Clipped the wires, cleaned the wire, used new heat shrink terminals, and reinstalled in same location.**

Alright, I was told this was the place to go to get the guys with the serious no BS answers. I just rebuilt an L92 I got as a rebuild able core. It has a rod knock. Had the engine completely checked over and refreshed by a local and very reputable machine shop. Drag, derby, and repair shops use and highly recommend them. They’re a bit pricey, but apparently they are the guys. They’re refreshed the block, punched it .010, line honed the cam and mains and installed the cam bearings. I had them rebuild the stock heads which they decked and installed a BTR spring kit and new valves. They supplied the main bearings. They assembled the rods, including 2 new and 8 new pistons (all factory stock).



I bought and installed:



GM Genuine 58x crank

BTR trunnion kit

BTR push rods

Melling HV oil pump

ARP Main and Head Studs

ARP Rod Bolts

Earls Steam Vent Kit(EAR-LS0041ERL)

Hastings Rings

MSD Blaster Coils with high current harness

Everything else is stock and all the important stuff is new.



The real, non-stock change is the Summit Stage 1 Truck Cam (SUM-K8718R1) and VVT Delete Kit (CMB-09-0027 with LS3 CMP sensor spliced into the L92 5 pin harness connector with phaser sensor wires cut clean and flush for sealing the plug.)



I used to be an Apache mechanic in the Army. We spent 3, methodical days putting this thing together. Anything that had a torque value or sequence got it. Anything that didn’t have one printed in the How To manual was referenced through Mitchell. When we finally installed the engine, I deleted the VVT in HP Tuners and fired it up. After about 30 seconds (I’m assuming entering closed loop) bank 2 sensor 1 started to drop and my fuel trims sky rocketed. It stayed that way until the engine warmed up. A professional engine builder told me his break in sequence, which I did. The cold start, bank 2 lean condition has never gone away. In fact, now it is worse because it will not come out of lean since I replaced the passenger exhaust manifold, gasket and donut. I have not even been able to idle MAF tune because I can’t get bank 2 out of lean. Here’s the thing though, the manifolds never get hot and the spark plugs are covered in coal.



Here is what I have done so far:



Systematically sprayed the entire engine with brake cleaner to look for a vacuum leak

O-scoped all the injectors at the injector’s control wire and back probed the X2 ECM connector

14.6v at the injector’s control pink wire

Checked for ground signal at the coils

Compression test - 180psi on all 8

Leak down test - I’ll post the numbers at the end

Pulled the fuel rail, blew it out to check for obstructions

Check each injector for the click

Swapped O2 sensors

Test fitted an O2 sensor from another L92

Swapped coil harnesses

Replaced Passenger exhaust manifold and copper sprayed the gasket(torqued 11 ft lbs then 15 ft lbs inside to out)

Replaced the collector donut twice, the second time with it smothered in high temp RTV(I was getting irritated at this point)

Fuel pressure tested the rail, matched the scanner

Cleaned all the block grounds and grounding points

I’m sure there might be a few other tests I did, but I can’t think of them now.



It just sucks because this is my family’s daily driver. We had to cancel half of our kids’ summer vacation trip because of this and lost probably close to $1,000 dollars in non-refundable campgrounds. If this would have been right, I would have had a week for tune and break in. We ended up renting a car to salvage what little was left of their summer. I am a high school teacher and I go back to work shortly after we get back and I’m just running out of time. This isn’t my first engine build, this isn’t above my skill level, but at this point I am completely lost. I know there have been a few posts on here about cold start bank 2 lean conditions, I’ve read them. So, here I am, going to the place where technical deep dives are just another Tuesday, looking for some insight on what I should check next when I get back home. Thank you for reading this and thank you in advance for your help.



Leak Down Results (less than 50 miles on the engine):



Cylinder

Observed Pressure

Leakage % = (100 − psi)

1

91 psi

9%



2

88 psi

12%



3

92 psi

8%



4

92 psi

8%



5

90 psi

10%



6

91 psi

9%



7

90 psi

10%



8

89 psi

11%

 

If you swap the injectors side to side, see if the lean condition follows... That would eliminate injectors. A smoke machine on the intake may help find a leak. Unmetered air would be what I'd look for.

 

I swapped injector 2 to injector 7, there was no change. If I had an unmetered air leak, wouldn’t that leave ashy white plugs and a glowing hot exhaust manifold, right?

 

Is this a swap vehicle? All else beside the cam stock?

Is it just misfiring on bank 2? The o2 sensor will see misfire as lean

 

Perhaps I missed something in your writeup but I would have swapped all injectors from one side to the other to test. Can you get temps on each exhaust port and see if any are cooler (not firing). Are any codes besides fuel trims being set? Does it sound like it's running on all 8 cylinders? There is a ground on the back of the drivers side head that will cause the coil packs on that side not to function properly if not grounded well.

 

It’s in a 2008 Yukon XL Denali. The old motor had 275,000 on it and it was tired.

When I unplug all the injectors on bank 2 the engine does not bog, cough, choke, burp, hiccup, or respond in any way. There is 0 change in performance. Unlike when I unplug any one of the injectors on bank 1, then it wants to die.

 

Well that sure sounds different than running lean... bank 2 isn't firing at all now? Look over the VVT delete wiring, you may have missed something.

 

From your description it sounded like bank 2 wasn't firing.

Make sure the coil subharness is going to the right coils.

Verify power and ground to the coils

Put the original coils and harness back on. Better anyway

 

I didn’t want to change too much at once. I figured if I just swapped one, that cylinder would show a change, and then on the right track, otherwise there was no need to move all the injectors. If I am wrong, let me know.

I can get individual cylinder temps and I will, but I can say the the entire manifold is touchable after about 5 minutes of high idle (850-1,000 rpm)

The only code it sets is a P0174 code.

the ground on the back of the driver’s head was cleaned and shiny as well as the mounting locations at the time of installation.

It definitely does not sound like it is firing on all 8 cylinders until it warmed up, then it was. Now, every once in a while it will cough like it’s trying to, but goes back to stupid.

 

Before I disassembled the old engine, I marked coil 1 and coil 2 to verify they returned to their original locations. They are currently installed that with coil 2 connector on coil 2.

 

I found the problem. The coil ground behind the power steering pump had corrosion under the sheathing. When I twisted that wire while checking grounds, the misfires went away. I snipped all 3 ground wires on that grounding point, cleaned the wire, and replaced the terminal ends with heat shrink terminals. Engine fired right up, B2S1 O2 started reading correctly and the short terms were trimming on both banks. Thank you all for your help.