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buick rainier
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My bet is that your DOD (Displacement on Demand) has gone bad. How the DOD works is there are oil passages that collapse the #1,4,6 & 7 Cylinder lifters, what happens is the lifters wear and they get jammed and will not release. I am not sure how or why, but that is what happened to me. Before this happens, usually you have a problem with one of those 4 cylinders (1,4,6,7) will keep fowling out the spark plug with oil.
The bad news is 99% of the Mechanics will tell you that your engine will need to have the intake, heads removed and replace the lifters. which is true, if you do it as per the book. However there is an easier way to fix it.
I did this and it worked perfect.
1) I was having #1 fouling issues, every 6 months I would have to change the #1 spark plug,
2) When replacing the spark plug no longer worked
3) I did a compression test, compression seemed fine, #1 was a little lower, something like 130PSI, The others were around 150PSI
4) Removed the (drivers side) valve colver, and discovered that the intake lifter was collapsed, I could wiggle the rocker.
5) Removed the intake, and then used this guy's tool worked like a champ, I broke my intake just as he showed,
6) I was not going to drive it so I sent my ECM to LT1 Swap and for $under $100 I sent him my ECM, he disabled DOD, and sent it back to me.
All in all I think I was around $400 in parts for everything, the tool, the ECM DOD delete, the intake gaskets, and the special tools I did not have to into the engine.

If you have a mechanic fix it, expect to pay $2500-$3000 as they will want to remove the entire top of the engine, replace everything, which is not a bad thing, but it seems much for a vehicle that is probably worth $3000.
 

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buick rainier
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It is literally a piece of steel rod, I think he hardens the end now... I had to use the Air tool like he showed there, I tapped and tapped, without luck, got the air scalier and removed the fingers, went to town, and after about 10-15 min the lifter finally popped out.. You have to remove the rocker BTW...
I literally did this on my 2006 and it worked like a champ.
 

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buick rainier
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Odd... Have you tried opening it on Youtube? There are a few videos on this, might take a little trial and error, but the procedure is the same.

More or less
1) Remove wires,
2) Remove valve cover (s)
3) find the stuck lifter (once the coils are disconnected, you can turn over the engine, and find the rocker and remove the rocker.
4) remove the upper intake and lower intake.
5) Once you know what lifter is stuck, you put the tool down into the oil passage and "tap" it until the lifter releases.
6) Break the tabs on the lower intake to deactivate the DOD mechanically
7) get the PCM reprogrammed to remove DOD electronically
8) Reassemble
 

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buick rainier
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IDK why the video is not working, it worked for me. might be an ad blocker or something you have going on. IF you look up this guy on Youtube, he has several videos on the process... I was fortunate enough that I did not need the vehicle so I took my time over a weekend... I do nothing fast.
 

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buick rainier
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He is using the rod to mechanically release the lifter. During operation Oil pressure collapses the lifters used for the DOD and are different than normal hydraulic lifters as they mechanically slide together to deactivate the valve. Over time, and in some cases abuse from infrequent oil changes they wear from the collapsing of them and they get stuck. You take the rod and it pushes on the lifter to separate the two pieces. It is a genius solution.

If you do this I would recommend changing the oil shortly thereafter as you will leave some shavings from the process...

Here is some information on DoD works Document ID# 1417658 2005 Ponti
 

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buick rainier
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1. Except for using oil pressure to release the lock-pins, these appear to be solid lifters, not hydraulic. There's no mechanism for hydraulic pressure to take up clearance from wear. At least, that's how your link describes them.

2. Either he'd beating on the lifter body, which doesn't bode well for the lifter roller, roller axle, or cam lobe; or he's beating on the lifter plunger which doesn't make sense since it's already in the collapsed position--and which doesn't bode well for the roller, roller axle, or cam lobe. Genius solution? Seems barbaric to me.

3. If the lifters get "stuck" from "wear", I'd think that the real solution is to replace them with lifters that aren't worn.

Is there something I don't understand?
1) They are hydraulic roller lifters, not solid. If they were solid this would not be an issue. Chevrolet engines used hydrualic lifters in 1955, and they started using the Roller hydraulic lifters in 1987. Solid lifters require adjustment about every 10,000 miles, thus the beauty of hydraulic lifters, no need to adjust the lash on them...
2) beating on the lifter is to release it, the second video I just posted yesterday he talks about how the lifter collapses and mushrooms then ends up getting stuck. Once you release it, you need to reprogram your ECM so that they no longer collapse. You also modify the pieces in the engine so that it longer activates as he shows in the videos.
3) Absolutely it is better to replace the lifter, BUT investing $500 and driving the car for another 100K vs $2500 for a vehicle that is barely worth $3000 does not sound like a good idea, especially when this fix will be forever, and never have to worry about this happening again.

I would say, yes, you do not understand what he is doing...
I did this very process on my 2006 and it worked like a champ, I drove it for thousands of miles afterwards and never had an issue.
I have a friend who is a full time mechanic, and I showed him this video and he was so grateful because it would save him a lot of time fixing this common issue and it would save his customers money.
 
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