Sparkies No Beno

[donjetman]

I bought this Yukon 2 mths ago and don't know its mx history.

Pulled the spark plugs today so as to soak my combustion chambers with solvent as part of TSB 10-06-01-008M(see this link)
https://f01.justanswer.com/ebrock63...il+Consumption,+MIL+ON,+Engine+Runs+Rough.pdf

My 6.2 L92 has 132k miles. How old to you think these these plugs are? It was purring like a kitten, never missed a lick, wasn't throwing any codes.

I got new ones coming, wires too, but I cleaned them up and plan to use them again someday.
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[iamdub]

What's their gap? They may not be so old, but if I was gonna guess, I'd say they were original. Usually, those types of deposits are from running fuel with lots of additives. How'd you clean 'em so well?!

 

[donjetman]

Chris, the gaps were .040" to .043". .040 is what they're suppose to be gapped at I think, so they weren't bad in that respect. I think all the grud came from all the oil its been burning because of the wrong valve cover and lack of an AFM oil deflector. At least that's what I'm hoping the problem has been since I'm doing all this work.

 

[donjetman]

I cleaned them up in my HF media blast cabinet, aluminum oxide and a wire wheel bench grinder.

These plugs are Iridium GM# 12571164 - ACDelco 41-985, which have now been superceded by 12621258 or 41-110.

 

[thompsoj22]

so if the plugs have that amount of combustion sediment how will you effectively remove the dissolved "solids" from the cylinders after the solvent turns them into a corrosive slurry? imo id rig up some kind of a shopvac and small tube to suction the majority of it out as opposed to simply cranking it out of the open plug holes. do you have a boroscope? how much is on the piston top's? i just dont like solvents in close tolerance friction areas. the blowby is solved, plugs cleaned/replaced maybe consider just leaving the crowns as they are and time will sluff the deposits off and out the exhaust? i have way to many opinions! your work/effort is professional and experienced but dont fix it til breaks? also since the exhaust is disconnected from the manifolds run the scope down there and check the cats for signs of clogging/deposits?

 

[donjetman]

do you have a boroscope

John, Yes I have a scope, but I'm not worried about it. I think whatever's in there will come out the exhaust sooner or later.

dont fix it til breaks

IMO it was broke. I was collecting 1 oz of oil for every 100 miles in the catch can I had installed not long ago. Maybe what I'm doing will help?

run the scope down there and check the cats for signs of clogging/deposits

There are fine screens upstream of the cats, they're probably a mess. I'd think to use a crow bar and turn them into HI FLOW cats, but I don't know how the ecm would like that? Where I live they don't do the sniffer thing for our annual inspections.
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[iamdub]

That's not a fine screen, that's the catalyst. OEM cats ARE "high-flow". Every tiny "hole" that you're looking at in those pics is the end of a "tube" of catalyst through which the exhaust flows. If you look at them head-on, it looks like a screen. Viewed from a slight angle, you can tell they're tubes. The PCM would throw catalyst inefficiency codes if you punched 'em out. It wouldn't affect fueling or anything, but you'd have an SES light on at all times.

 

[iamdub]

Chris, the gaps were .040" to .043". .040 is what they're suppose to be gapped at I think, so they weren't bad in that respect. I think all the grud came from all the oil its been burning because of the wrong valve cover and lack of an AFM oil deflector. At least that's what I'm hoping the problem has been since I'm doing all this work.

I would expect burned oil to be black instead of ashy deposits. But, maybe synthetic oil burns like that. You use synthetic?

 

[swathdiver]

Never in my life have I seen spark plugs like that. Never ever never. Don't know what to make of those.

The cats are taking a beating. You can hollow them out but will need to turn off the lower O2 sensors with a tune or do or buy those things that trick them into thinking the cats are still functional.

I'm running 41-985s in mine and the original set came out looking about like your last photo.

 

[iamdub]

People pay good money for used OEM cats. If you don't have visual inspections and want them gone, either get headers or have both entire cats cut out and replaced with pipe.

 

[donjetman]

You use synthetic?

I don't know what the previous owner put in it? I just bought it from a used car lot 2 mths ago and it had a recent WallyWorld oil change sticker on the windshield. I WILL run synthetic.

 

[Tonyrodz]

People pay good money for used OEM cats. If you don't have visual inspections and want them gone, either get headers or have both entire cats cut out and replaced with pipe.

Sold my stock Y pipe with cats for $150.

 

[iamdub]

I don't know what the previous owner put in it? I just bought it from a used car lot 2 mths ago and it had a recent WallyWorld oil change sticker on the windshield. I WILL run synthetic.

I thought I recalled reading that you had just bought it before diving into all of this. At least all the plugs looked similar.

 

[iamdub]

Sold my stock Y pipe with cats for $150.

There was an OEM Y-pipe from a 2011 (?) Suburban on craigslist about a month ago. The guy replaced it because he couldn't get the rear O2 sensors out. He was asking $100 or best offer cuz he just wanted it gone. I thought for sure I could've sold the cats for more than that and made money on it. I would've made it a bolt-on catless OEM Y-pipe for my Tahoe then sold it's Y-pipe and/or cats and would've made a decent chunk to put towards long tubes. Or Christmas.

 

[Tonyrodz]

There was an OEM Y-pipe from a 2011 (?) Suburban on craigslist about a month ago. The guy replaced it because he couldn't get the rear O2 sensors out. He was asking $100 or best offer cuz he just wanted it gone. I thought for sure I could've sold the cats for more than that and made money on it. I would've made it a bolt-on catless OEM Y-pipe for my Tahoe then sold it's Y-pipe and/or cats and would've made a decent chunk to put towards long tubes. Or Christmas.

Guess you didn't get it?

 

[thompsoj22]

John, Yes I have a scope, but I'm not worried about it. I think whatever's in there will come out the exhaust sooner or later.

IMO it was broke. I was collecting 1 oz of oil for every 100 miles in the catch can I had installed not long ago. Maybe what I'm doing will help?

There are fine screens upstream of the cats, they're probably a mess. I'd think to use a crow bar and turn them into HI FLOW cats, but I don't know how the ecm would like that? Where I live they don't do the sniffer thing for our annual inspections.
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Every task that you have completed has been a dealer equivelant repair of an existing issue, but you are doing better work because you cant pay a 9 to 5 mech to treat your equipment as though it was there own. the AFM baffle will hopefully have you at 5k oil changes with minimal consumption. We did another ca to sedona az loop, 1300 miles, averaged 18.7 mpg in complete comfort/safety and our daughter watching movies with the headphones while wifey listens to xm! these vehicles are amazing and im at 131k miles! You are going to love your "urban limo" when its completed.

 

[donjetman]

You are going to love your "urban limo" when its completed.

I love the way it rides and drives. Soon we plan on taking it to the CO mtns and back(2000 miles) when I get er done.

 

[iamdub]

Guess you didn't get it?

No. It would've been yet another part stored in the shop and forgotten. I'm currently focused on a suspension revamp/upgrade.

 

[donjetman]

*UPDATE* - Changed spark plugs today.

Today I installed a set of ACDelco # 41-962 plugs. I removed ole obsolete ACDelco 41-985 plugs that I had cleaned up(see pics in post# 1 here) and re-installed back in Dec of 2018 when I had first purchased the vehicle with 131k miles. Back then it was burning and leaking oil like crazy. Folks here told me to install a catch can. This showed me it was catching an oz of oil every 100 miles. This amount of oil being sucked into the combustion chambers had "stuck" the piston rings. It also needed a rear main seal. I did a little research and discovered TSB# 10-06-01-008M: TSB# 10-06-01-008M So I did the valve cover update, installed the bypass deflector, and did an extra long piston/combustion chamber soak with Gunk brand "Motor Medic". I also replaced the rear main seal.

Today vehicle has 171k miles, it doesn't need any makeup oil between extended changes, the catch can doesn't catch much of anything, and it's dry as a bone underneath.

Below is a pic I took "today" of the ole plugs that I pulled out. They have 40k more miles since I cleaned them(see pics in post# 1) and no sign of oil burning. YEAH!

 

[wsteele]

Pretty prrfect…