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2008 GMC Envoy Denali

n8in8or

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Not really a lot to show for it, but I made some solid progress tonight. I got the harness run down the transmission and plugged in where it needed to be. I installed the O2 sensors in the headers......which I found out would have been much easier BEFORE I installed the headers. Then I ran the fuel lines down the tunnel and plugged in and bolted them up. With those tasks done then I could install the trans mount and bolt down the motor mounts. The driver side mount was a piece of cake to drop the bolts down into, but the passenger side was a real pain!! When I built them I thought I’d be able to fish the bolt plate down with a magnet and I’d be set. Nope. Not that easy. I struggled over half an hour to get them in. If I was to do it again I would weld nuts to the mounts and run bolts through from underneath. Oh well. It’s done. Now it’s sitting on its own and I can continue to reinstall bits tomorrow.

52CA223C-59E7-4733-AE29-0C41FE5FE67A.jpeg6949F920-D7F8-4075-A85A-13D2329E93BF.jpegBF903C77-7DF0-4A24-90B9-75FB147F4496.jpeg555292DC-9D1E-4C75-B824-74B50B1050FC.jpeg80DF4EDC-A3AA-48E8-A56A-AB076054184A.jpegCDD3886E-07BB-4A73-82BE-EEB0AC28555D.jpeg
 

n8in8or

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Today’s progress:

First thing I did was do a little painting. I wanted to touch up the front coolant crossover pipe with the Motor Coater......and since the paint was out I figured I might as well take care of one last eye sore: the throttle body. It was mildly corroded and discolored, and since it’s front and center it seemed a little dress up was in order.

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Before:

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After:

CB78C409-01CE-4C0D-9F71-D4CD9E7BB80E.jpeg
 

n8in8or

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The rest of the work today was underneath the truck. First up was installing the transfer case. But before I did that I installed the front drive shaft. I noticed clearance was tight between it and the driver side header....conveniently that’s right where the balance weight is located on the shaft. So I took a hammer to the header to make a small clearance dent.

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Here’s the clearance after the transfer case was installed and the front shaft was in its home.

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After finishing rear driveshaft installation I moved on to exhaust installation. The Y pipe that came with the headers went in easily and fit nice.

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I applied pressure with a floor jack to get it as high as possible. It hangs just a little below the crossmember. This shouldn’t be a problem.

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I also installed the DEI heat sleeve on the trans cooler lines.

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After some struggling with the vent hoses on the trans and transfer case I was pretty much done underneath. I got the front axle shafts put back into place. The last thing I could think of underneath was putting the good oil filter on in place of the crappy STP one I used for masking purposes. I went with a Hastings LF641 based on what I read the fanatics over at Bob Is The Oil Guy say about it.

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Tomorrow will be engine compartment work. There’s still a chance I’ll have it running tomorrow, but we’ll see.....I didn’t get as far today as I had hoped and tomorrow I have some custom work like new battery cables and a new air intake so that stuff will be time consuming.
 

n8in8or

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Today didn’t end as far as I hoped, but that happens.

First thing I did was install the intake manifold. Then I did the throttle body and this was when I noticed my first problem.... I forgot that I had broken the clip on the plug during disassembly. So tomorrow I need to hit the junkyard and cut one off of a harness.

TB Plug.jpg

After that I started working on installing accessories and cables. I chose a good spot on the block to use as my main ground attachment point. I made a new 1/0 cable to run from the negative lug on the battery to the block. I bought some Rockford Fosgate batter stud extenders for connecting to the battery.

Ground Block.jpgGround Batt.jpg

I made a 6 gauge cable running from the block to the body in a new location from stock.

Ground Body.jpg

I also made a 6 gauge cable running from the block to the frame, also in a new location from stock.

Ground Frame.jpg

Next I worked on the positive cables. I terminated the starter cable at the correct length and wrapped it in DEI split loom. Then I made a new 2 gauge cable from the alternator to a 150 amp Optifuse circuit breaker. The output from the circuit breaker is also a 2 gauge cable and it goes to the positive post on the battery. All 2 gauge is wrapped in DEI split loom. Last new cable was a 6 gauge one from the battery to the input of the fuse block. It's kinda cramped......

Pos Alt.jpgPos Batt 2.jpgPos Batt.jpg
 

n8in8or

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After battery cables I installed plug wires. I noticed the passenger header was kind of close to the frame, so I added some heat shield to the frame to keep the paint from burning. You can also see in the pic that I used DEI plug boot protectors to protect the MSD wires from the heat. I need to buy stock in DEI!

Header Heat.jpg

Then I continued to put the accessories together. I put the tensioner for the AC belt on and noticed a big oops.... I ordered the wrong harmonic balancer!! I forgot that this had a small secondary belt for just the AC compressor and the balancer that I bought had just the one pulley on it. I'm pretty sure I know what I need buy to correct it, but I'm going to call ATI this morning to confirm. The bummer is that to add the second pulley I have to pull the balancer of the hub and the hub off the crank snout, so that's going to be fun. Another delay.....

Pulley Oops.jpg

Here's the stock crank pulley for comparison:

Pulley Oops 2.jpg

So this is where it sits at this point. I still have a few days of work left, hopefully it's together and running by the end of this week.

Front View.jpg
 

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FRANKENBURBAN
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Trucks used a deslugger because they have a low mounted piston compressor. I've never heard of problems on trailblazers because they use a scroll compressor instead of a piston compressor. One thing a friend of mine did tell me was to not use the tensioner, instead step up to the later model which used a 1 time use stretch belt. It is a pain to get them on since you have to take the compressor loose, but he said that was what he found to be the fix for the trucks with compressor belts coming off from slugging.
 

n8in8or

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Trucks used a deslugger because they have a low mounted piston compressor. I've never heard of problems on trailblazers because they use a scroll compressor instead of a piston compressor. One thing a friend of mine did tell me was to not use the tensioner, instead step up to the later model which used a 1 time use stretch belt. It is a pain to get them on since you have to take the compressor loose, but he said that was what he found to be the fix for the trucks with compressor belts coming off from slugging.
Cool, thanks for the info.
 

n8in8or

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Today started off with me calling ATI to see what the solution was for my AC pulley situation. From what I could see online yesterday, there was an additional pulley I needed to buy that goes on the backside of the damper. That was true. What I didn’t know was that there were some bolts I also needed to order separately, so that alone made it a worthwhile call. After telling me what I needed they asked me if I had ordered direct from them before.....I said no. I told him I bought it through Summit originally....and he said, “Oh they’re a vendor, yeah you should buy through them again because you’ll save money and get free shipping”....NICE! So he gave me all the part numbers I needed and then I ordered from Summit. I should hopefully have all the stuff I need for the balancer tomorrow. I will definitely support ATI in the future.

Today during lunch I hit the junkyard. I was able to find 3 pigtails with the connector piece I needed (I got extras in case I screwed the repinning up since I’ve never done it before). I figured out how to disassemble the connector and then reassembled the old wires in the “new” connector. Much nicer than splicing 6 wires - cleaner and faster.

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After that I removed the balancer so I could get ready for reinstallation tomorrow.

Finally I worked on the heater hoses - routing them and cutting them to length. Got them all wrapped with various DEI products too.

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n8in8or

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It’s alive!! Got it together enough to fire (used the stock air intake just for convenience). No weird noises, but not running smooth.....not sure if it’s just because it needs a tune or if something else is wrong. The header tubes for cylinders 4 and 6 got hot, but the rest were cool to the touch. No raw gas smell though. So it’s interesting. I’m going to talk to the tuner tomorrow to get his thoughts.

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n8in8or

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Unequal fuel from those 2 injectors?
Take #2 and #1 and swap them, see if heat continues from #2 or if it follows injector.
I thought you were going to tell me to start cracking injector lines one at a time....
😁

Talked to the tuner this morning. He isn't too concerned about how it's running....he said the computer could be that lost, but he does want me to check the basics. He suggested disconnecting the injectors and listen for even compression while cranking (simple compression test....which is much appreciated since some of those plugs are a real bear to get to. And then he also wants me to check for vacuum leaks. So I'll do that stuff over the next couple days. I also need to make the new intake for it and finish installing the fascia, headlights and grill. If everything with the engine checks out, then I'll take it to him first thing Monday morning. Fingers crossed!!
 

n8in8or

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I started it and ran it for 30 seconds this morning before work. It sure sounded like it's dropping a cylinder or more. After shutting it off I checked the header tubes.... 3,5 and 2 were hot and 8 was warm. Just for funsies I looked it up....the Active Fuel Management disables cylinders 1,4,6&7......quite a coincidence. I'm still going to check the basics to make sure I don't drop something off to the tuner that needs a basic piece of maintenance that costs him time and me money.

The other thing I thought of: before starting it last night I cranked it 3 times for a long time with the coils unplugged. I didn't realize that this didn't also disable the injectors (I thought it was smart enough to detect that, because you know, computers....). So there is a chance that maybe it was slightly flooded and fouled the plugs? I doubt it because for 1, it started pretty quickly when the coils were plugged back in and 2, I don't smell raw fuel right now which I would think I'd smell if a plug or 4 were fouled. Still something else to double-check. It's easy to pull the number 1 plug and take a look at it.
 

n8in8or

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Tonight’s findings:

With injectors unplugged it cranked over smooth. Seemingly not a compression issue.

I pulled the #1 plug. Sure doesn’t look fouled.

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I ran it with the scanner hooked up and sprayed all around the intake and there was no change to O2 readings. Looks like no vacuum leaks.

And while looking at the scanner I noticed that there were codes for the 4 cylinder deactivation solenoids being an open circuit. Doesn’t seem out of the realm of possibility that the computer shuts off the injector and coil to that cylinder if there’s a cylinder deactivation solenoid failure.

And then I finally tried putting the trans in gear for the first time. The truck just creeped forward and the engine wouldn’t go past idle....and then it would finally kill the engine and not let you restart it for a period of a minute or so. So the computer is just not happy. I feel really confident my problems are all tune related. Unfortunately not driving is going to make loading and unloading the truck on the trailer a bear. Ah well.

I finished up tonight starting on the new air intake. I have a piece of 4” aluminum pipe that I had a nipple welded on at work (I NEED TO GET MY OWN TIG) and a 4” 45 degree and 90 degree elbow. I kind of pieced things together and it looks like I have a rough game plan. I need to modify the filter opening and make a 4” elbow for between the filter and MAF to really make it work. I’ll be working on that more over the next couple days.

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FRANKENBURBAN
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What injectors are you running? If it has the stock 08 5.3l injectors, they won't be big enough. the 5.3l in 08 only got a 29.4 lb/hr injector at 58 psi. The tbss got a 42 lb/hr injector. The 5.3l injectors are only supposed to be good to 400hp at the wheels, and thats pushing it on straight gas. The flex fuel injectors of that time were supposed to be 54 lb/hr.
 

n8in8or

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What injectors are you running? If it has the stock 08 5.3l injectors, they won't be big enough. the 5.3l in 08 only got a 29.4 lb/hr injector at 58 psi. The tbss got a 42 lb/hr injector. The 5.3l injectors are only supposed to be good to 400hp at the wheels, and thats pushing it on straight gas. The flex fuel injectors of that time were supposed to be 54 lb/hr.
Hmmm, are you sure about that? I looked them up in the parts catalog when I was first planning the build and they come up as the same injector as the Trailblazer SS and I just looked them up again and they are listed the same.
 

n8in8or

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I did some more digging. Both the 08 Envoy Denali with the 5.3 LH6 and the 08 TBSS with the 6.0 LS2 are listing the 12580681 (Delco 217-1621) injector. These do appear to be rated at the 29.4 lb/hr at 58/60 psi you referenced above. I guess the tuner will tell me what the duty cycle is and we'll take it from there.
 
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