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Discussion Starter #1
Hello everyone! I just purchased a used 2008 Enclave CXL for $2500 on craigslist. It is in decent shape for the price. It has about 184k miles and the engine was replaced about 5 years ago. Not sure how many miles are on the new engine, but both the front and rear seals need replacing so likely a lot. I think the tranny has the waveplate issue even though it has probably been repaired before, as it shudders when driving with light to moderate throttle. There is a code I cannot seem to track down the cause of... 1175, Fuel trim cylinder balance bank 2. I have several live data captures that show the two O2 sensors with a difference most of the time. I have replaced coilpacks, moved around injectors, replaced the MAP sensor, cleaned the MAF sensor, replaced the bank 2 O2 sensor, replaced all spark plugs, and checked for vacuum leaks. There is a small vacuum leak still where the tube from bank 1 valve cover goes to the intake plunem. I tried using epoxy to seal it, but it looks like it may still have a slight leak. Just not sure that would cause the difference between the banks. Any help would be greatly appriciated. I really want to get this car restored to a reasonably dependable state.
 

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the 2008s have a motor mount that is vacuum assisted. It has a hose running to it.


Im wondering if during the engine rebuilds-- the hose was left off-- or a motor mount with no vac assist was used.. leaving that hose unplugged.


On the 2008 Acadia, they did not use the vac assisted mount- and the intakes manifolds nipple, was simply capped off.
as the vehicle aged- that little cap covering the nipple- either fell off (after routine maintenance) or dry rotted- allowing a vacuum leak--- it caused rough running engine.
Wed point the owners to check- and sure enough the cap was gone or leaking. capping it off- and engine worked fine again.


Id check that hose....
 

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Discussion Starter #5
Fantastic recommendation. Thank you! I had no idea about the vacuum assist on the mount, although I am not surprised. There seems to be a big push to reduce/eliminate vibrations in gas engines at this time. I wonder how much it has to do with electric cars and how quiet and smooth they feel when driving. I'll check that hose assembly and report back. Thanks again!!
 

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Discussion Starter #6
Ok folks, I went ahead and just eliminated the vacuum motor mount system by removing its connection from the intake and attaching my vacuum gauge directly to the port. I should have done this sooner, but I am reading low vacuum, 14 to 15 at in Hg at idle. Interesting thing is, as soon as the AC pump kicks on, the vacuum jumps up to 16-17 in Hg. In addition, I see the difference in the trim banks disappear when the AC pump is engaged. As soon as the AC pump disengages, a 4% to 5% difference appears.

Questions...

Does the low vacuum automatically mean worn rings?

Could this be attributed to a bad VVT component? I am seeing unusually high misfires on cylinder 6.

Thanks!

P.S. I like the upgrade!
 

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Discussion Starter #7
Still working on this problem...
I think there may be an issue with the head on this engine. I get a pretty consistent misfire on cylinder 6. I have replaced the coil, plug, and injector on this cylinder with no change.

Any idea if I can replace the bank 2 head without removing the engine from the car???

Any help appriciated on this.

Thanks!
 

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Discussion Starter #9
Rbarrios,

I have still not figured it out.

It feels like one cylinder may be down possible due to a bad intake valve, but I am not sure. Mostly runs ok except a small miss and the check engi e light.

Another symptom I see is the Catalytic converters are running at different temps. The Bank 1 cat is consistently 40 degrees hotter.
 

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Discussion Starter #10
Forgot to mention Bank 2 is the one with the 1175 code on it. The long term fuel trim is higher in Bank 2 which fits that the cat is running cooler.

Are there any tests I can run that will eliminate the injectors as the issue?
 

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I am no auto mechanic but have dealt a lot with my 2008 Outlook and now have a 2015 Enclave. Running the vehicle with that cylinder not firing properly will introduce more raw fuel into the cat which may damage it in the long run. What kind of scanner do you use? The only thing I know which will determine exactly where the problem lies is either a Tech 2 which GM mechanics use, a Snap-On or similar. I have a blue driver and it does a decent job but not on the true diagnostic level to a particular component. You can bring it to a dealer and pay just a diagnostic fee or to a independent mechanic.
In the meantime, make sure that you vacuum leaks are taken care of, make sure your air intake is clean, throttle body is clean and free. Make sure that your PCV orifice is clear. Run a bottle of Techtron concentrate through one, and probably two tankfuls, if you do not use top tier gasoline and maybe even some injector cleaner. Always Use Top Tier fuel.
 

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If you suspect carbon buildup on a intake valve then you may want to consider using the CRC Intake valve valve cleaner.
 

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Discussion Starter #13
I'm not sure if it is carbon. I did a leak down and it seemed like air was always coming back out through the intake.

Keep in mind this is a 2008 engine so not DI.

I will try it anyway however since it seems like an inexpensive option to just try.

The engine has wear on it but it does seem like it still has some life in it. Seems to produce a good deal of power and runs great other then issues mentioned. The rear seal ended up NOT being the source of the oil leak. I replaced the front seal and found that the nylon washer on the oil pan plug was split from being tightened too much. I put a new one on and no more leak!

Also found that the harmonic balancer was falling apart. The oil leak at the main front seal was soaking the rubber in the balancer for years. It was about to fly apart.

Anyone ever try to take off just the bank 2 head with the engine in the car? Just wondering if I could disassemble the timing chain enough to get the head off. I sure would love to be able to repair the head without taking the engine out. Probably not going to happen though.

Thanks everyone!
 
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