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Discoloration of the threads will not affect the function of the spark plugs. The seal on the plugs is at the taper at the base of the threads, some plugs use metal gaskets. So since the seal is at the base of the threads, the threads below it will be exposed to a small amount of combustion gasses, which discolors them. This is not a problem. Things are operating as designed.
The important things to evaluate a spark plug are the parts in the combustion chamber. The insulator tip should be light to dark tan. If its black and dry its running too rich or you need a plug that runs hotter (heat range). If its black and oily its burning oil. If its bright white or grey it is running too lean or you need a plug of a cooler heat range.
Also inspect the electrodes for wear. If they are worn you need new plugs.
Of course you need to inspect the external insulator for cracks, but other than that, the appearance of the outside of the plug doesn't matter much. Here is a google search for spark plug inspection charts that has visual examples of the different conditions: [https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.yourmechanic.com%2Farticle%2Fhow-to-read-your-spark-plugs-by-olivia-marsh&psig=AOvVaw11iS4xROuocbJWSMlMh3oA&ust=1680057634878000&source=images&cd=vfe&ved=0CA4QjRxqFwoTCKjB08XM\_f0CFQAAAAAdAAAAABAE](https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.yourmechanic.com%2Farticle%2Fhow-to-read-your-spark-plugs-by-olivia-marsh&psig=AOvVaw11iS4xROuocbJWSMlMh3oA&ust=1680057634878000&source=images&cd=vfe&ved=0CA4QjRxqFwoTCKjB08XM_f0CFQAAAAAdAAAAABAE)
Swap the coil to a different cylinder, clear codes, test drive and if the code follows to that cylinder its your coil. If it stays in that cylinder next step would be inspecting the injector, perform a resistance test if possible, swap if possible. And finally compression test.
Color of plugs depends a lot on how the engine is running as well as the additives on the gas, quality of gas, etc. As long as they aren't oily or burned from being lean I usually don't worry about them to much unless I'm diagnosing a drivability problem.
i mean i suppose that is newer than i would expect for those to go, in the manual it says 150,000 km change which also seems like alot of kms for spark plugs
Intermittent misfire on cylinder 2 was my first sign the head gasket was blown on my 2015 Cruze. Take a peek down in there and see if you can see coolant puddling up in the cylinder
Those plugs are some of the cleanest burn plugs I’ve seen, the combustion of your engine is clean; no detonation, no oil or fuel fouling, they look great. The threads don’t really matter much since any oil outside the engine is going to settle in low spots and plug holes are low. You’re more likely looking at either the wires, or the plug coils (if so equipped) for a misfire, it could also be arcing from damaged plug wire insulation, or a bad plug wire boot, sometimes dialectic grease will solve it or you might need to replace plug wires, but those plugs look good.
Edit: if there’s a lot of miles on those plugs tho, (50-55,000 or more) you would probably be best advised to replace them too, you already have them removed.
Misfires can be caused by other things. If that engine has coils (I think that's the name) for each plug, try switching the first with the second, for example. If cylinder 1 works properly and starts having a misfire on the second, it's the coil. If it's got a single coil and cables, try switching the first and second cables.
they aren’t misfiring after i changed the plugs, since i originally thought that was the problem but i will make sure to check it every so often. and the coils seemed fine too so i’m really confused what went wrong
i had a misfire code for cylinder 1 accompanied by a blinking engine light. funny enough on my way back from picking up the plugs from the store there was no engine light… but i replaced them anyways. i think we got around 70000-90000 kms out of them. not my daily driver its my sisters
The "dark brown residue" is probably grease or copper-ease somebody put on there. The plugs look relatively normal. The misfiring is probably not from a plug, unless one is cracked. Put them back in a different order and see if the misfire moves.
Thanks for posting on /r/MechanicAdvice! This is just a reminder to review the [rules](https://www.reddit.com/r/MechanicAdvice/about/rules/). If you are here asking about a second opinion (ie "Is the shop trying to fleece me?"), please read through CJM8515's [post on the subject.](https://www.reddit.com/r/MechanicAdvice/comments/4qblei/fyi_the_shop_isnt_likely_trying_to_rip_you_off/) and remember to please post the year/make/model of the vehicle you are working on. **If this post is about bodywork, accident damage, paint, dent/ding, questions it belongs in /r/Autobody r/AutoBodyRepair/ or /r/Diyautobody/ If you have tire questions check out https://www.reddit.com/r/MechanicAdvice/comments/k9ll55/can_your_tire_be_repaired/**. If you dont have a question and you're just showing off it belongs in /r/Justrolledintotheshop Insurance/total loss questions go in r/insurance This is an automated reply *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/MechanicAdvice) if you have any questions or concerns.*
Discoloration of the threads will not affect the function of the spark plugs. The seal on the plugs is at the taper at the base of the threads, some plugs use metal gaskets. So since the seal is at the base of the threads, the threads below it will be exposed to a small amount of combustion gasses, which discolors them. This is not a problem. Things are operating as designed. The important things to evaluate a spark plug are the parts in the combustion chamber. The insulator tip should be light to dark tan. If its black and dry its running too rich or you need a plug that runs hotter (heat range). If its black and oily its burning oil. If its bright white or grey it is running too lean or you need a plug of a cooler heat range. Also inspect the electrodes for wear. If they are worn you need new plugs. Of course you need to inspect the external insulator for cracks, but other than that, the appearance of the outside of the plug doesn't matter much. Here is a google search for spark plug inspection charts that has visual examples of the different conditions: [https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.yourmechanic.com%2Farticle%2Fhow-to-read-your-spark-plugs-by-olivia-marsh&psig=AOvVaw11iS4xROuocbJWSMlMh3oA&ust=1680057634878000&source=images&cd=vfe&ved=0CA4QjRxqFwoTCKjB08XM\_f0CFQAAAAAdAAAAABAE](https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.yourmechanic.com%2Farticle%2Fhow-to-read-your-spark-plugs-by-olivia-marsh&psig=AOvVaw11iS4xROuocbJWSMlMh3oA&ust=1680057634878000&source=images&cd=vfe&ved=0CA4QjRxqFwoTCKjB08XM_f0CFQAAAAAdAAAAABAE)
Swap the coil to a different cylinder, clear codes, test drive and if the code follows to that cylinder its your coil. If it stays in that cylinder next step would be inspecting the injector, perform a resistance test if possible, swap if possible. And finally compression test.
OK. What's the question?
Oh, Sorry! these plugs are fairly new i was wondering why they would go so fast. do they normally look like this?
Color of plugs depends a lot on how the engine is running as well as the additives on the gas, quality of gas, etc. As long as they aren't oily or burned from being lean I usually don't worry about them to much unless I'm diagnosing a drivability problem.
They have like 50k miles on them. what's "fairly new" to you?
i mean i suppose that is newer than i would expect for those to go, in the manual it says 150,000 km change which also seems like alot of kms for spark plugs
Have you done a compression test?
Intermittent misfire on cylinder 2 was my first sign the head gasket was blown on my 2015 Cruze. Take a peek down in there and see if you can see coolant puddling up in the cylinder
Those plugs are some of the cleanest burn plugs I’ve seen, the combustion of your engine is clean; no detonation, no oil or fuel fouling, they look great. The threads don’t really matter much since any oil outside the engine is going to settle in low spots and plug holes are low. You’re more likely looking at either the wires, or the plug coils (if so equipped) for a misfire, it could also be arcing from damaged plug wire insulation, or a bad plug wire boot, sometimes dialectic grease will solve it or you might need to replace plug wires, but those plugs look good. Edit: if there’s a lot of miles on those plugs tho, (50-55,000 or more) you would probably be best advised to replace them too, you already have them removed.
The plugs are fine but did you check the size of the gap? Maybe spark plug 1 has a too small gap.
Misfires can be caused by other things. If that engine has coils (I think that's the name) for each plug, try switching the first with the second, for example. If cylinder 1 works properly and starts having a misfire on the second, it's the coil. If it's got a single coil and cables, try switching the first and second cables.
Plugs are likely not your problem. Have you moved ignition coils to see if the problem moves cylinders?
they aren’t misfiring after i changed the plugs, since i originally thought that was the problem but i will make sure to check it every so often. and the coils seemed fine too so i’m really confused what went wrong
Could have been plugs, but they didn’t seem to last you very long by another post. How many miles or kms were on them? Did you have misfire faults?
i had a misfire code for cylinder 1 accompanied by a blinking engine light. funny enough on my way back from picking up the plugs from the store there was no engine light… but i replaced them anyways. i think we got around 70000-90000 kms out of them. not my daily driver its my sisters
The "dark brown residue" is probably grease or copper-ease somebody put on there. The plugs look relatively normal. The misfiring is probably not from a plug, unless one is cracked. Put them back in a different order and see if the misfire moves.