3 burnt spark plugs - why?
08-23-2016, 07:49 PM
#1
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3 burnt spark plugs - why? Ok experts...
2008 c6 LS3
3 of the original Iridium '100,000mile rating' plugs had burnt the iridium tip right off! Interestingly all the others look fine. Normal or what would cause this?? (read on)
The 3 tips that disintegrated were at the back of the engine by firewall (2 from drivers side and 1 from the passenger side).
34,000 miles on the clock total, but I would suspect the mods added in the past year might be the cause; (aprox. 1,800 Miles) Longtube headers, KB intake, ported TB and mail-order tune with 160* stat and i run 91 or 93 fuel.
Also, the last 600miles or so were driven with the electric water pump conversion, so im not sure if that might have created any air voids or hot spots?
or how about;
Clogged fuel injectors?
Bad tune?
air leak?
In the photos you can see a comparison of the burnt off tip.
Car seems to run fine except has seemed to recently develop an intermittent rough idle (especially when hot). Not sure if thats related.
I also attached a new plug after driving it hard for the week and so far it looks ok but what is that white build up??
2008 c6 LS3
3 of the original Iridium '100,000mile rating' plugs had burnt the iridium tip right off! Interestingly all the others look fine. Normal or what would cause this?? (read on)
The 3 tips that disintegrated were at the back of the engine by firewall (2 from drivers side and 1 from the passenger side).
34,000 miles on the clock total, but I would suspect the mods added in the past year might be the cause; (aprox. 1,800 Miles) Longtube headers, KB intake, ported TB and mail-order tune with 160* stat and i run 91 or 93 fuel.
Also, the last 600miles or so were driven with the electric water pump conversion, so im not sure if that might have created any air voids or hot spots?
or how about;
Clogged fuel injectors?
Bad tune?
air leak?
In the photos you can see a comparison of the burnt off tip.
Car seems to run fine except has seemed to recently develop an intermittent rough idle (especially when hot). Not sure if thats related.
I also attached a new plug after driving it hard for the week and so far it looks ok but what is that white build up??
08-23-2016, 08:38 PM
#2
Looks like your plugs are running too hot. The white build up on the new plug and the melted electrodes are symptoms of this.
I think your tune is not correct for your mods. I would take the car to a local competent tuner who can dial it in. I suspect your car is running lean and or the ignition timing is off.
You need to get this corrected or you will eventually destroy your engine.
I think your tune is not correct for your mods. I would take the car to a local competent tuner who can dial it in. I suspect your car is running lean and or the ignition timing is off.
You need to get this corrected or you will eventually destroy your engine.
08-23-2016, 11:41 PM
#4
Those plugs are too hot and the tune is a bit on the lean side. Also the rear cylinders don't flow coolant well so that may be a contributing factor since you installed an electric water pump.
I would install standard copper NGK TR6 plugs for starters. Run the car moderately hard and check them a few times. If they begin to look like the plugs in the pictures get the car retuned.
I would install standard copper NGK TR6 plugs for starters. Run the car moderately hard and check them a few times. If they begin to look like the plugs in the pictures get the car retuned.
08-24-2016, 09:12 PM
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Those plugs are too hot and the tune is a bit on the lean side. Also the rear cylinders don't flow coolant well so that may be a contributing factor since you installed an electric water pump.
I would install standard copper NGK TR6 plugs for starters. Run the car moderately hard and check them a few times. If they begin to look like the plugs in the pictures get the car retuned.
I would install standard copper NGK TR6 plugs for starters. Run the car moderately hard and check them a few times. If they begin to look like the plugs in the pictures get the car retuned.
To clarify, you think the issue might just be plugs heat range and might not be starving for fuel?
Ok, TR6 sounds like a easy thing to try. Oh but I forgot to mention to the thread that the new iridium plugs (see attached above) were superseded from the originals and i wonder if they are 'a bit colder' now because they are just slightly shorter insulator.
The old plugs were AC delco 41-985 12571164 I just read that they are commonly found on 4.8's and other older LS engines and the new superseded plugs are 41-110 12621258 designed for 2005+LS.
Do you think i should switch to TR6 right away or try the new plugs a bit longer?
Last edited by 99firehawk; 08-24-2016 at 10:46 PM.
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08-25-2016, 12:08 AM
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Interesting read, although it does mention that its a dyno reading where-as the engine needs to be shut off immediately after the wot run. However the basics might be applicable?
http://cochise.uia.net/pkelley2/sparkplugreading.html
...The article shows the 'base ring' -black indicating rich condition and thats how mine all look, which confuses me on why i might be running lean then?
Also I think this article illustrates the heat range 'past the curve on the strap' as being too hot of a plug and thats how my plugs look meaning they are too hot of a plug.
It would be neat if that solves it, but im sure there might be more to the story
http://cochise.uia.net/pkelley2/sparkplugreading.html
...The article shows the 'base ring' -black indicating rich condition and thats how mine all look, which confuses me on why i might be running lean then?
Also I think this article illustrates the heat range 'past the curve on the strap' as being too hot of a plug and thats how my plugs look meaning they are too hot of a plug.
It would be neat if that solves it, but im sure there might be more to the story
08-25-2016, 12:40 AM
#9
spend $150 on a wideband before the $X999 engine explodes and before bumping the thread to chase your tail around in circles
plugs take on an appearance that averages the running condition, plus or minus any significantly abnormal/improper indicators. If you spent 98% of the time driving in closed loop and 2% of the time at WOT, you will see 98% of the color from the closed loop condition and the other 2% is showing up as melted ****.
plugs take on an appearance that averages the running condition, plus or minus any significantly abnormal/improper indicators. If you spent 98% of the time driving in closed loop and 2% of the time at WOT, you will see 98% of the color from the closed loop condition and the other 2% is showing up as melted ****.
08-25-2016, 01:52 AM
#10
Sure he could buy a wideband, but that isn't going to show what the 3 cylinders he is having an issue with are doing. Unless he installed o2 bungs in each of the header primaries.
To me the other 5 cylinders look fine, maybe a touch lean but like an aggressive tune type of lean.
The back 3 plugs look like the cylinders are too hot which is causing detonation. Cooler plugs will help.
Also since this problem has shown itself since you recently installed the electric water pump. There may not be enough coolant circulating causing the rear cylinders to be too hot in the first place.
To me the other 5 cylinders look fine, maybe a touch lean but like an aggressive tune type of lean.
The back 3 plugs look like the cylinders are too hot which is causing detonation. Cooler plugs will help.
Also since this problem has shown itself since you recently installed the electric water pump. There may not be enough coolant circulating causing the rear cylinders to be too hot in the first place.
08-25-2016, 04:13 AM
#11
Sure he could buy a wideband, but that isn't going to show what the 3 cylinders he is having an issue with are doing. Unless he installed o2 bungs in each of the header primaries.
To me the other 5 cylinders look fine, maybe a touch lean but like an aggressive tune type of lean.
The back 3 plugs look like the cylinders are too hot which is causing detonation. Cooler plugs will help.
Also since this problem has shown itself since you recently installed the electric water pump. There may not be enough coolant circulating causing the rear cylinders to be too hot in the first place.
To me the other 5 cylinders look fine, maybe a touch lean but like an aggressive tune type of lean.
The back 3 plugs look like the cylinders are too hot which is causing detonation. Cooler plugs will help.
Also since this problem has shown itself since you recently installed the electric water pump. There may not be enough coolant circulating causing the rear cylinders to be too hot in the first place.
08-26-2016, 10:03 PM
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Ok after some reading about how to read sparkplugs and closer appraisal of all the plugs, i think im convinced that there is some detonation occurring. Im basing on I notice speckling on the insulator and pitting on the strap and its more redish-color. All of the plugs have these symptoms.
I also think the black soot is an indicator of maybe oil blow by or too rich. Im not sure what i think of that yet.
This photo is magnified and its difficult to see the pitting in person.
Last edited by 99firehawk; 08-28-2016 at 09:37 PM.
08-27-2016, 04:12 PM
#14
Judging by the close up picture you definitely do need some tuning corrections. The colder TR6 plugs will help a marginal amount as well... I've seen detonation peppering on comepletly stock LS1's, 2's, 3's and 5.3's with the factory heat range plugs.
08-28-2016, 09:33 PM
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...Then again, some website like this one make my plug look ok lol. (however not much detail).
http://www.aa1car.com/library/reading_spark_plugs.jpg
Regardless, with the speckling we know they're hot.
i picked up the TR6's today and hopefully i can swap them tomorrow night.
http://www.aa1car.com/library/reading_spark_plugs.jpg
Regardless, with the speckling we know they're hot.
i picked up the TR6's today and hopefully i can swap them tomorrow night.
08-30-2016, 10:55 PM
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I swapped out the already new AC Delco iridium 41-110 plugs out with TR6's tonight.
TR6's appear to be gapped at around .35 or .40 is that good for my mods?
The iridium's i took out only had 2 weeks of driving use (I would guess at maybe 100 miles or less), i snapped pics of them because each side of the engine had the same carbon pattern forming on each plug; similiar to the tips burning off, the furthest rear cylinders illustrate a black ring but no carbon build up, then as you move forward towards the front they gradually get to be a full ring of carbon film. See pics. Pics are in order from rear to front.
Im sure after a while they will all have a full carbon but regardless it does show as you move aft the fuel mixture or heat or air seems to change right?
They also had just started speckling which i learned is the insulator starting to boil.
the TR6 should help with the 'black speckling' i hope.
TR6's appear to be gapped at around .35 or .40 is that good for my mods?
The iridium's i took out only had 2 weeks of driving use (I would guess at maybe 100 miles or less), i snapped pics of them because each side of the engine had the same carbon pattern forming on each plug; similiar to the tips burning off, the furthest rear cylinders illustrate a black ring but no carbon build up, then as you move forward towards the front they gradually get to be a full ring of carbon film. See pics. Pics are in order from rear to front.
Im sure after a while they will all have a full carbon but regardless it does show as you move aft the fuel mixture or heat or air seems to change right?
They also had just started speckling which i learned is the insulator starting to boil.
the TR6 should help with the 'black speckling' i hope.
Last edited by 99firehawk; 08-31-2016 at 09:36 PM.
09-01-2016, 11:57 AM
#17
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I personally would have gone with a TR5 copper plug. I don't think you are at the point of needing to step down to a colder plug. Your issue is entirely in your bunk mail order tune.
09-03-2016, 11:28 PM
#18
Once you start getting upwards of 400hp, TR6 plugs, regardless of what style plug you decide to run, are a good investment. Variations in fueling per cylinder depending on how old your injectors are could cause some plugs to be worse then others, variations in the cooling system could cause one cylinder to run hotter then another, so its a balancing act. I decided to make the jump from TR5 to TR6 after 1500 miles on my plugs and they showed signs of lighting off the ceramic portion. But my system isnt lean, this is heat related detonation your seeing here from the firing end getting too hot. The complete black ring around the bottom of the plug shows that the AFR is within spec and the position of the discoloration on the ground strap shows whether or not your spark advance is a bit low or high. Granted there is a more exact science to this because your supposed to make a pull and shut the car down and then pull the plugs but you can get "tips" off of reading your plugs regardless if they start showing unusual wear with very few miles.
09-04-2016, 10:03 PM
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Well i don't disagree, the timing might indeed be too advanced.. But i do think a colder plug is not a bad thing to experiment with based on what i have read. Hotter plugs can help contribute to high temperature detonation and i think that is evident in the black speckling on the insulator. The TR6's were super cheap anyway, i couldn't believe it lol! Oh, and the vette provides much easier access to to all the sparkplugs without having to go from underneath, so its no big deal to swap them back out. So far the TR6' feel good, and theres a solid coating of carbon on my exhaust tip that seems to form a lot quicker than the iridium's...
I read the thing maybe to watch for running a colder plug is carboning up, what are your thoughts on the disadvantages?
Years ago I had TR55's in my old LS1 firehawk which it happened to have audible 'pinging' detonation but the 55's weren't helping or causing for that matter either.
09-04-2016, 10:31 PM
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Once you start getting upwards of 400hp, TR6 plugs, regardless of what style plug you decide to run, are a good investment. Variations in fueling per cylinder depending on how old your injectors are could cause some plugs to be worse then others, variations in the cooling system could cause one cylinder to run hotter then another, so its a balancing act. I decided to make the jump from TR5 to TR6 after 1500 miles on my plugs and they showed signs of lighting off the ceramic portion. But my system isnt lean, this is heat related detonation your seeing here from the firing end getting too hot. The complete black ring around the bottom of the plug shows that the AFR is within spec and the position of the discoloration on the ground strap shows whether or not your spark advance is a bit low or high. Granted there is a more exact science to this because your supposed to make a pull and shut the car down and then pull the plugs but you can get "tips" off of reading your plugs regardless if they start showing unusual wear with very few miles.
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The car is a 2008 with about 33,000mi on it with bolt ons, around 430rwhp. TR6 recommended right?
Do you really think it needs new fuel injectors considering the carbon pattern on all 8 is exact same on the opposite bank to eachother? I would think bad injector would randomly stick out like a sore thumb?
I agree with the cooling system theory.
In the time of this thread I have actually read about mostly everything you just mentioned.
To clarify the full black ring signifies a good AFR, so does that mean full black ring as seen in the first pic without carbon build up? Or the last pic which is the front of the engine with full black ring and full ring of carbon film build up?
Its difficult to get a clear interpretation of the timing strap but some have it just after the curve in the groundstrap (between the bend and the threads), and others have it right in the middle of the curve.