Failed compression test, what to do now?

[Jkust]

Hi all, I have 9-7x that I bought many years ago when it was just a few years old and drove for many years and I was storing it in my garage so my son could drive it when he got old enough. It sat for about a year and a half and I pulled it out of the garage and it ran great for one day. I would start it periodically during the time it was stored as well.
The second day after getting it out of storage when I started it to use it, it had a cylinder 4 misfire, which in this case the cylinder wasn't firing at all.
I took it in hoping it was a coil, plugs or wires or an injector, but instead it failed the compression test at 25lbs and I took it home with no advice given from the shop as soon as they realized they weren't going to make any money.
It ran poorly like this one time before I parked it and I put in some fuel injector cleaner and fixed it quickly.
This time that isn't working. The car has about 125,000 miles on it and was my commuter car for years and had an easy life. So now i'm sitting with a car that is undrivable and I don't know what to at this point. It runs but only on 7 cylinders and smokes white smoke like crazy.
What could possibly be wrong? It gave no warnings at all, no noises or anything?

Thanks all.

 

[Mooseman]

I'm willing to bet it's a failed AFM lifter. And #4 cylinder is one of the affected ones so likely is your issue. Do you hear a loud clacking noise from the valve cover? This video shows what happens and even a way to possibly fix it.

My only other recommendation on top of what he did would be to leave the VLOM unplugged so that way it won't try to deactivate those cylinders at all until you get it tuned. Another way would be to unplug the vacuum sensor on the brake booster. It's also used for the AFM. But you will have to get it tuned to turn off the CEL.

 

[TollKeeper]

I agree with @Mooseman . I just have never seen an engine go from running perfect, to blah, in a day, without some help from a failed part.

Edit: I will add that you can do the hopeful repair, as shown in that video, but it does require tearing the engine down the the Valley Pan, and hoping that the shock will reset that lifter, and then running a kit to block off the rest of the system, and then getting the DOD code deleted.

 

[Jkust]

So, I really don't have the time or wherewithal to deal with this problem. As a last effort, i tried a can of intake clean in the unlikely event that would have helped. It seems to idle a bit longer at at 1k rpms before you can really feel the miss and the check engine light is on steady instead of blinking and then quickly settles back to missing and shifting hard.
It's a shame really the car still looks like a new car on the inside as I never had any passengers. Looks like I will need to to donate it or sell it cheap. Interestingly enough, the engine doesn't actually make any extra noises under the hood while running other that the engine shaking a bit more than normal. I see it's not too hard of a job to replace a single lifter if you have the time and inclination.

 

[TollKeeper]

Selling cheap? Like how cheap? Been wanting a 9-7x with a 5.3 for a long time... Where you located?

 

[Jkust]

Selling cheap? Like how cheap? Been wanting a 9-7x with a 5.3 for a long time... Where you located?

Couple grand, haven't decided what to do with. Where are you at? I see the miles are pretty low for the age when looking at them online. Forgot to ask why is there heavy white smoke coming out when driving or sitting that smells like raw gas? Oil looks good but smells like gas and it isn't filling up with coolant/not increasing level on dipstick and the coolant reservoir remains full?
Still can't understand why the engine makes no extra noises, no clicks or ticks. The engine just shakes a little more than normal when looking at it under the hood and is as normal sounding as any engine. The x factor seems to also be whether the cam shaft lobe is damaged assuming it was is a lifter. Wanting to also not think that the white smoke is a cracked head or head gasket. There is no sweet smell in the exhaust and can't imagine suddenly the head is also cracked simultaneously to the lifter going out.

 

[TollKeeper]

Im in Denver... At a couple grand thou, I would pass. Im going to have to drop 2-3g just in a new engine. and at a couple grand, the cost factor becomes more than the trucks value.