Hello, I have been trying to problem solve my 2010 acadia for over a month now and had been in the dealer for 2 weeks and they can not figure it out either. The original issue was p0300, p0302, p0304, p0306, p0430. The issue destroyed the engine, catylitic converter on bank 2 and o2 sensors. I purchased a 2017 3.6 llt vin D replacement engine with 2000 miles, catylitic converter and o2 sensors to put in it. The engine was complete with all sensors and manifolds. The only thing I replaced was the intake manifold because the 2017 has a plastic intake and the throttle body position would not connect to my air box. With the newer engine installed the computer is still throwing the same codes. Any ideas? The dealer said it could be the ecm or power going to bank 2 fuel injectors. To add to the frustration the dealer melted my new cat, o2 sensors and engine mount.
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This a GM dealership?

This is a red flag:

It is very simple to check power to the injectors......

Another thing is, it seems to be a problem with the even numbered coils/injectors.....

How was the engine destroyed?

Yes it is a GM dealership. The engine popped bank 2 cylinders. Water in oil fill cap and coming out the exhaust. Which is what I thought destroyed the bank 2 cat.

I don't know if water would melt a cat, but it certainly wouldn't help it any.

I agree with Tech II, sounds like your dealership doesn't diagnose well, and will likely cost you extra money. That said, if they're doing the job for $500.00 and every other dealer quoted $5,000.00 then you might come out ahead.

Excessive misfires can do a lot of things, but usually the hard parts survive it and the cats melt. Excessive detonation can crack pistons etc. What do you mean exactly by "popped bank 2 cylinders"?

How many miles are on this car?

I don't know what (if anything) starves first on the 3.6 . How is the fuel pressure?

The engine lost compression in bank 2. I am guessing that the misfire in bank 2 cause that along with the cat and the either cracked head or head gasket. The car has 140000 miles on it and we live in the mountains so figured she just had enough climbing 4000 ft up every day to go home. That'* why I decided to just replace the motor instead of rebuilding it. Plus the cost was way less. As for the dealer now they say there is some kind of electrical problem causing the misfire. They are now going to check the injectors and coil packs then the ecm. They are $129 an hour so I am a little worried to see the bill on this one.

Losing compression on an entire bank of cylinders is unlikely without major overheating or other damage/neglect. Did the dealership tell you that compression was lost on all cylinders 2, 4, and 6? I would find it extremely difficult to believe that you have two engines that lost compression on the same three cylinders. You should ask how many PSI each cylinder showed.

Was the original engine diagnosed with a cracked head or head gasket? What test(*) did they do to discover that there is a cracked head or head gasket leak? Did they do a compression test on it? What are the PSI numbers? Did the engine ever run hot?

This is where I think a lot of us are confused. And concerned. Bank 2 has three cylinders of your V6 engine. The firing order is 1-2-3-4-5-6, so on your engine it appears to be firing:

1 good
2 misfire
3 good
4 misfire
5 good
6 misfire

What is common between cylinders 2, 4, and 6 that is not common to cylinders 1, 3, and 5? Cylinder head, cams, cam phasers, fuel rail, electrical controlling injectors and coils. That'* about it. So:

Cylinder head: Never goes out on all three cylinders at the same time such that misfires are detected but the engine isn't overheating or destroyed by oil and coolant and exhaust getting places they shouldn't.

Cams: Never become mechanically defective across the entire cam at the same time and at the same time only cause some misfires.

Cam phasers: Never go so far out of phase that misfires are detected but desired cam phasing versus measured cam phasing doesn't post its own trouble code(*).

Fuel rail: Low pressure would cause misfires. High pressure too, but that is unlikely.

Electrical controlling injectors and coils: Shorts, breaks, water, corrosion, dirt/dust, and other damage can cause issues with electrical. Perfect conductivity across all electrical paths is required for the engine to run well. All of your issues are on Bank 2, which is on the front of the engine. All of the water and dirt/dust that gets to an engine gets to the front of the engine first. Much less of it gets to the back of the engine.

An engine will usually drive along for a long time with a misfire and never crack a head or blow a head gasket, unless there are other contributing factors such as heavy towing, abusive application of power, etc. Does any of this apply to your driving?

Otherwise what often happens is the fuel that is noy completely burned gets burned in the catalytic converter. The catalytic converter, not designed to process so much fuel, gets extra super hot and melts the core. Often the melted chunk of core is pushed to the outlet side of the housing and plugs the exhaust path.

I have one of these in an Outlook with over 150,000 miles on it, and it shows no signs of anything like this. It has always lived at 5,000-6,000 feet, has often been up to 11,000 feet, and even once went to over 14,000 feet. It has been down to near sea level once in its life. Here'* the fun thing about altitude on naturally-aspirated engines: cylinder pressures go down as the car goes up. There is more revving as there is less air, however, heat contribution, cylinder pressures, and thermal stress go down. The fact that you are climbing a hill means heat contribution can accumulate more quickly, but that is fairly-well handled by this platform. Also, keep in mind that for all of the extra work going uphill, there is a bunch of extra relaxation for your engine going downhill.

About time. They need to check the wiring leading to the injectors and coil packs.

This is the concerning part. A misfire is likely a coil pack going bad on this engine. Since it is three cylinders I'd personally change my mind towards electrical feeding this half of the engine. This misfire could cause a catalytic converter to melt. Unless you drove it this way for months or years up and down your 4,000ft hill you shouldn't have compression issues.

I'm not there so my criticism may be misplaced, however, the dealership should have diagnosed what could have caused a misfire first, before replacing the engine became a possibility. Perhaps they have, and the details
haven't been completely relayed here. Just being fair. If you have compression-test results from the original engine, my concerns would be greatly assuaged.

It appears to me that the core problem remained with the vehicle while the engine got replaced. From my perspective I'd suggest towing your car to a different shop. Diagnosing the misfire AFTER replacing the engine is the scariest part of this situation to me. A seemingly blank-check to the dealership is running a close second.

Thank you all for the info. I live at 6000ft and we climb 4000ft over 10 miles to get home. Some parts are very steep and took a while for my wife to understand that the motor had to cool down before pulling it into the garage. She understands now after I had the rear main seal replaced cause it warped the aluminum plate causing a leak. The vehicle drove great for a few more years but recently had a misfire but would go away after clearing the codes. This happened a couple of times before bank 2 started completely misfiring and she tried to climb up the mountain but it lost all power. So I towed it home. This is when I replaced the engine and cat. The misfire doesn't go away with the old engine so I was told by GM that the dealer had to relearn the computer. Now I am in a holding pattern waiting on the dealer. Trying to do my own homework on it to see if it is the wiring from the fuse box or failure in the ecm. I am thinking about buying the harness and ecm and trying to problem solve it myself or just getting rid of the vehicle.

I don't know the psi on the old engine. But new something catastrophic happened to the old engine after seeing water coming out of the exhaust and oil fill cap. The misfire had to cause the cat to melt and probably did the other damage. I have a warranty on the new engine so at least I have that going for me if they did any damage to it while testing it and melting the new cat and o2 sensors.

If you don't mind my asking: What part of the US do you live in?

Shouldn't be a big deal unless it is hard-climb lots-of-throttle then skid to stop in garage with no idle time. A couple of minutes of idle should make up for anything like that.

I've never heard of this on the GM 3.6 . Wondering if any of the other guys here have . . . ?

Also, was this diagnosis done by the same dealer as the current engine-misfire stuff?

That seems like a stretch. When the cause of the misfire is repaired, the PCM will figure it out. It doesn't say "I had a misfire on 2, 4, and 6 so I will make sure those cylinders misfire until a human tells me otherwise".

FWIW should take them ten minutes to trigger a relearn.

. . . or fuel pressure or wiring between PCM and coils, or wiring to injectors . . . ?