2012 Yukon XLT with mystery rough idle and misfire codes

gotliebk

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Better invest in a catch can to keep that oil out of the intake. Once you find out what is wrong here of course.
Good idea. Any brands that you recommend? Should I get a direct fit or a universal and make my own brackets?
 

gotliebk

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Sorry if I sounded kind of pedantic on the extended oil change interval thing, but I think these AFM engines are kind of a different breed as it pertains to oil cleanliness and reliability of the DoD lifters and oil manifold, at least in the earlier generation versions. But it only matters that you have confidence in your process.

Did the shop indicate where the leak down was failing (bottom or top end)?

Anyway, it sounds like you are going to go about it in a very methodical way, so best of luck.

I agree with the advice to send an oil sample to Blackstone, it is a very check diagnostic data point and very reliable.
I got very little information back from the dealer. On the printout they gave me it reads, "PERFORMED COMPRESSION TEST - TEST GOOD AT 135 - PERFORMED LEAK DOWN TEST - LEAKING DOWN ON #3 CYLINDER - HAS INTERNAL PROBLEMS - CUSTOMER DECLINED AT THIS TIME" Needless to say I was underwhelmed by the details I got back. I had waited 5 days to get a 7am appointment for the airbag and diagnostic. It took them three days to complete the airbag replacement and the diagnostic with really crappy communication from the service coordinator. For my education, what's the difference between bottom and top end failure?
 

wsteele

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I got very little information back from the dealer. On the printout they gave me it reads, "PERFORMED COMPRESSION TEST - TEST GOOD AT 135 - PERFORMED LEAK DOWN TEST - LEAKING DOWN ON #3 CYLINDER - HAS INTERNAL PROBLEMS - CUSTOMER DECLINED AT THIS TIME" Needless to say I was underwhelmed by the details I got back. I had waited 5 days to get a 7am appointment for the airbag and diagnostic. It took them three days to complete the airbag replacement and the diagnostic with really crappy communication from the service coordinator. For my education, what's the difference between bottom and top end failure?
I might try and find another shop to work with, that one is a loser.

If you have a compressor, one of these gadgets can be pretty useful when debugging cylinder issues.

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Geotrash

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As for the extended cycle on the oil changes, I've been doing that for 20+ years on all my vehicles (98 Suburban with 290K, 06 Monte Carlo with 249K) with very good results. This particular vehicle made it to 180K before it began exhibiting any problems at all. If it turns out this is a mechanical wear issue, I will end up rethinking the extended change cycle for the oil.
One more detail on this: There is some evidence that AFM failures are much more common in engines with extended oil change intervals. It's a complex system and it doesn't take much sludge or debris to interfere with the operation of the VLOM or the lifters. Most mechanical components in an engine can tolerate extended oil changes, but the AFM system is more sensitive to dirty oil. While your issue isn't on an AFM cylinder, it's worth mentioning anyway.
 

gpracer1

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Have someone else do a leakdown on #3 or do it yourself, find out where it is leaking out and if it really is. In the mean time maybe swap the coil with one from the other side of the engine just to eliminate that.
 

gotliebk

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So I took my 2012 Yukon to a specialty shop and had them redo the diagnostics. Got a lot more detail this time around but the same diagnoses.

From the shop:
Note:
Checked For Injector Pulse and Spark Pulse. Found Good. Listened To Injector With Stereoscope and And Compared To Other Injectors. Sounds The Same. Performed Compression Test. Cylinder 3 150psi. Checked Cylinder 1 150psi. Found With in Spec. Listened To Rocker Arms With Stethoscope. On Cylinder 3 Makes Excessive Clatter Noise. Removed Valve Cover To Inspect. Put Dial Indicator On Tip Of Rocker Arm On Cylinder 1 and Cylinder 3. Found That Cylinder 3 Has .030 Less Lift. Indicates Issue With Worn Cam Shaft and Lifters. Rec Replacing Cam Shaft All Lifter, Lifter Cups and Vlom. Check Valves and Valve Guides After Heads Are Off.

Now for the painful part. They recommend I replace the camshaft (for wear) and all the lifters, gaskets, and VLOM. Here is their quote:

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Does this analysis make sense? Does a .03" difference in lifter travel enough to make a valve not seal? Any other way I can address this?
 

wsteele

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So I took my 2012 Yukon to a specialty shop and had them redo the diagnostics. Got a lot more detail this time around but the same diagnoses.

From the shop:
Note:
Checked For Injector Pulse and Spark Pulse. Found Good. Listened To Injector With Stereoscope and And Compared To Other Injectors. Sounds The Same. Performed Compression Test. Cylinder 3 150psi. Checked Cylinder 1 150psi. Found With in Spec. Listened To Rocker Arms With Stethoscope. On Cylinder 3 Makes Excessive Clatter Noise. Removed Valve Cover To Inspect. Put Dial Indicator On Tip Of Rocker Arm On Cylinder 1 and Cylinder 3. Found That Cylinder 3 Has .030 Less Lift. Indicates Issue With Worn Cam Shaft and Lifters. Rec Replacing Cam Shaft All Lifter, Lifter Cups and Vlom. Check Valves and Valve Guides After Heads Are Off.

Now for the painful part. They recommend I replace the camshaft (for wear) and all the lifters, gaskets, and VLOM. Here is their quote:

You must be logged in to see this image or video!

Does this analysis make sense? Does a .03" difference in lifter travel enough to make a valve not seal? Any other way I can address this?
It sounds like these guys are a bit more forthcoming with the details of their diagnostics. A few things that still leave me a little cold.

A lack of lift doesn't affect the seal of the valve. Lift is opening of the valve (unsealing), if you had no lift, you can still have a perfect seal.

They don't know if you have any cam lobe issues at all. You have to remove the head to see the cam lobes. A bad lifter might be all you have going on. Replacing all the lifters and the cam for a single bad lifter is well, expensive.

Your VLOM is the updated one. You didn't have an AFM lifter problem, why do you need a new VLOM?

$2200 labor is very high for this job, even as spec'ed which may end up being a fraction of what they are quoting (if the cam is fine).

Parts - look like more than 100% markup from online retail like GM Parts Direct.

If it were me, I would keep looking for a shop. A dealer service department quote likely would come in close to this and they probably would give you a lower bound number as well, if they found that the cam was fine. If the cam turned out to be OK and it was just a bad lifter, I would likely have them replace the lifters on that bank and leave the other bank alone (i.e. not even pull the head). That job would probably be a faction of the quoted labor as well.
 
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gotliebk

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It sounds like these guys are a bit more forthcoming with the details of their diagnostics. A few things that still leave me a little cold.

A lack of lift doesn't affect the seal of the valve. Lift is opening of the valve (unsealing), if you had no lift, you can still have a perfect seal.

They don't know if you have any cam lobe issues at all. You have to remove the head to see the cam lobes. A bad lifter might be all you have going on. Replacing all the lifters and the cam for a single bad lifter is well, expensive.

Your VLOM is the updated one. You didn't have an AFM lifter problem, why do you need a new VLOM?

$2200 labor is very high for this job, even as spec'ed which may end up being a fraction of what they are quoting (if the cam is fine).

Parts - look like more than 100% markup from online retail like GM Parts Direct.

If it were me, I would keep looking for a shop. A dealer service department quote likely would come in close to this and they probably would give you a lower bound number as well, if they found that the cam was fine. If the cam turned out to be OK and it was just a bad lifter, I would likely have them replace the lifters on that bank and leave the other bank alone (i.e. not even pull the head).
I've never pulled a head on a vehicle but there is a first time for everything. If I pulled the head, how would I know if the cam is worn or not? We are talking about .03" on one lobe. How do you measure something round to that kind of tolerance? Also, how do you know I have the updated VLOM? Is it by the year/model? Thanks for your input here. I'm facing a big decision on this vehicle and I can use all the insight I can get.
 

wsteele

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I've never pulled a head on a vehicle but there is a first time for everything. If I pulled the head, how would I know if the cam is worn or not? We are talking about .03" on one lobe. How do you measure something round to that kind of tolerance? Also, how do you know I have the updated VLOM? Is it by the year/model? Thanks for your input here. I'm facing a big decision on this vehicle and I can use all the insight I can get.
The 2012 model year came with updated VLOM and AFM lifters. I believe they actually started shipping them in mid-2011. Maybe the shop always replaces all lifters, the VLOM, etc. when they find a problem lifter. Given your problem wasn't a collapsed AFM lifter, it would appear your VLOM and AFM lifters (V4 mode) are working fine. I just found it odd they would feel the need to replace it.

You aren't going to have .030" of "normal wear" on a cam lobe. That is more than half the lift of the whole lobe, so it is going to be a kind of binary thing. Either the cam lobe is going to look normal (looking down at it, after the head, lifters and trays are removed), or it is going to looked all scored and damaged. Frankly you will probably know when the problematic lifter is removed. If the roller looks fine and normal, the cam will almost certainly look the same.

We have had a couple of members in recent weeks find lifters where the roller was damaged and the cam obviously as well (the roller rolls on the cam lobe). One was a guy where one of his lifters roller had seized and did a job on the cam lobe. He too had lost lift and found the problem with a misfire on that cylinder. He had to replace the cam and lifter (decided to do them all). More recently we have a very experienced member who had replaced his lifters and cam and had a bad lifter tray cause his lifter to turn, causing it to damage both the roller and cam lobe. Again he is replacing the cam and lifters (along with the bad trays).

In your case, you don't know yet. I believe in guys fixing their own cars, but unless you have a fair amount of mechanical experience, what your journey of discovery might entail could be more than maybe a guy who changes his own oil might want to bite off. If you had a real gear head friend you could entice to come over and lend a hand, then I would probably say go for it, because even the full job as described by the shop isn't outside the skill level of one and a half gear heads. The difference in price would be a lot. The parts to do everything the shop said they would do would likely come in about $1500, so that and enough beer to keep your friend coming back probably gets it done. If you two found just a bad lifter, under $500 would likely get you back on the road with all new lifters on that banks side.

For a guy who has never pulled a head, my advice would be to keep looking for a good (and reasonable) shop. You know enough now to know what the minimum and maximum the job might entail.

BTW, all of the above is just one guy on the internet's opinion.
 

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