Check your spark plugs NOW! THIS is what caused the P0300 code on my C7 Corvette!

[@HorsePowerObsessed]

You guys asked for more information on the plug failure and here it is! Definitely an interesting find. I'm super glad I did this extra testing because knowing the real reason is a real relief! Thank you all! 👍👍

[@billsharp1815]

Good job on testing the spark plugs, very informative Justin

[@HorsePowerObsessed]

@@billsharp1815Thank you!

[@ProtectiveDadPranks]

There are fake Car Guy KZbinrs out there and then there is Horsepower Obsessed!

[@HorsePowerObsessed]

My MAN!!

[@billsharp1815]

Totally agree with you Steve 👍

[@robertherd3653]

Yeah we know EXACTLY who the fake car guy is. Should I say the fake corvette guy who doesn’t even have a corvette! 🤦🏽‍♂️

[@stephenr115]

Yes sir!

[@stephenr115]

Display bad plug on garage wall!

[@marct9360]

Good info. If the O2 sensor turns out to be bad, it should be covered under the emissions warranty. The firing end of the plug is called an electrode, not a diode. Since the plug was shorted to the outer shell then it would not be firing at all because the spark would be grounded to the block. Therefore there would be some raw fuel going into the exhaust system which could cause a problem with the cat on that side.

[@richardelliott8352]

glad I read this before watching another corvette video from someone who can't even describe a spark plug

[@DadsGarageDIY]

Really good test. I wouldn’t have guessed a plug. I was leaning towards a wire.

[@HorsePowerObsessed]

Especially after I changed them out I was really uncertain because they LOOKED fine but sometimes the problem is under the surface as shown here.

[@DadsGarageDIY]

@@HorsePowerObsessed Yep. Crazy that happened. But, glad you figured it out.

[@paullomonaco5260]

Always full of information thanks so much once again

[@HorsePowerObsessed]

Thank you!!!

[@HBFBajaRacer]

Well, good thing I did headers. Swapped the plugs and wires when I was there lol

[@HorsePowerObsessed]

Always a good idea!

[@robertjakicic5878]

Excellent detective work Brian!!

[@jamesnelson7415]

That plug has a broken insulator inside the plug body. The insulator is basically a ceramic tube surrounding the cathode insulating it from he outer shell of the plug. Most likely, ot was dropped prior to installation and the cracking worsened over time and use. BTW, the electrical components of a spark plug are the cathode and the anode, a diode is, essentially, a one way gate for electrical current, not fund in spark plugs, although resistors are found in nearly all street car spark plugs to reduce

[@davebest6369]

Glad you are doing this too. Great info, thanks Justin

[@HorsePowerObsessed]

My pleasure!

[@stevenloewen8875]

Just had the P0300 code come up on my 2017 C7. I was thinking it wasn't the spark plugs as it only has 8000 miles on it, but I just changed them and it runs fine now.

[@ppeller3]

Good job inspector Cluezo!👍🏻

[@HorsePowerObsessed]

🫡

[@leedimatteo5078]

wow man, the plug even looks good, the meter test confirms!!

[@HorsePowerObsessed]

💯

[@billmiller8782]

Justin - great info - and great job. Truthfully - you went further than the avg mechanic - even at the dealership. If anything you gave yourself more evidence when trying to make a warranty claim. Hopefully - they will make all parts replacements and service free of charge under your warranty -- as the problem was caused directly by a bad plug -- too bad you did not label each plug as to what cylinder they were out of.

[@HorsePowerObsessed]

I appreciate it. I really just wanted to get info out to the public about it because it is obviously something that can happen to any C7 out there.

[@DHenry-cs8up]

Nice find HPO. I didn't know measuring the resistance from top to bottom on a spark plug could cause an issue. Great information.

[@marct9360]

They added the resistance to spark plugs to help suppress radio noise. That's what the stands for at the beginning of the part number for the plug. For example, the part number that I use for my '73 is R45TS where the R stands for resistance and the TS stands for projected tip, tapered seat.

[@craigthescott5074]

Does this affect the C7 Z06’s?

[@HorsePowerObsessed]

Yes. All of the C7s use these plugs.

[@Sick_ridz]

I wonder with the plug shorting to the aluminum block if that will jack up your alternator too. That alternator is grounded to the block too. I cant imagine stray voltage hitting the block can be good for anything grounded

[@HorsePowerObsessed]

So far, it’s good.

[@jordannelson9266]

My ‘17 C7z seems to be having this exact same issue. Hopeful that this is the fix. It was in the dealer for new pulley, tensioner, belt, and water pump last week (few days before the p0300 code came up) so I am hopeful that the dealer’s work didn’t cause this issue somehow 😅. Only 16k miles on mine, similar to your mileage I think?

[@HorsePowerObsessed]

Very similar mileage. It is pretty common for these plugs to get fouled it seems.

[@jordannelson9266]

Ended up needing a new block 😅 Dealer had the car 4 times and did nothing to fix. Took it to a vette shop. They found abnormal gouging/wear on cam, lifters, etc and some extremely fine metal in the oil. I verified their findings myself. I thought these were supposed to be reliable 😂. I think you have some presence in south Florida so I recommend you avoid Autonation Chevrolet in Lake Worth!

[@KenHilger]

Your bad plug also had whiter porcelain than the other 7; less heat in the spark maybe. Your removal video showed some porcelain shots and may define the cylinder.

[@HorsePowerObsessed]

I’ll definitely check it out. To be honest though I don’t think it matters a whole lot I just wanted to make sure one of the plugs was bad and we confirmed that here today.

[@vettesweetnos]

I always measure my plug before putting it in. The ladies seem to appreciate the measurements.

[@HorsePowerObsessed]

lolololol

[@issiahsilva]

If you gotta measure it, it ain’t big enough 🤣

[@vettesweetnos]

@issiahsilva nah, have to make sure it fits first lol

[@stephenr115]

I know this isn’t problem but @scottykilmer said if you leave car running when putting gas in trips a code; I don’t know if spark plug code but interesting point I never leave car running filling gas but I have years ago

[@marklagasse2012]

I had lean bank one code on my c6z. It wasn’t necessary but I changed both o2 sensors just so they would be done in a pair. Like not changing one plug for a misfire change them all.

[@HorsePowerObsessed]

That’s exactly what I plan on doing

[@marklagasse2012]

I would think they would be warranty also since emissions driven

[@jeffstieren4474]

Excellent job

[@HorsePowerObsessed]

Thanks!

[@drewpackard6646]

Good job Justin 👍🏽

[@FrontSeatDriver]

Great information, Justin!!

[@HorsePowerObsessed]

Glad it was helpful! I appreciate the support as always Jason!

[@drbooo]

great video HPO

[@HorsePowerObsessed]

Thank you!

[@jayjones3254]

Curious, do you have to "gap" the new plugs? or straight outa the box?

[@HorsePowerObsessed]

You should always check them but these ones came pre-gapped and they were accurate.

[@brianw8963]

It is odd that it did not show the specific cylinder misfire. Did You clear the 420 code after replacing the plugs, and it came back? It would have had to run for a long time to compromise a cat, but if the downstream 02 sensor is good and it still gets the 420, the cat is probably bad. I think You put a different exhaust on it at some point, which would not effect the cats. But we all know how they like to void warranties when they see aftermarket parts. Hope that is not the case for You. Good luck, will be interesting to see the outcome. Also Jason, pull your engine oil dipstick out and give it a good smell and even remove the fill cap and give it a wiff. If you smell any gasoline at all, change the oil. If there is any gas in the oil, this will also cause fuel trims to be messed up.

[@HorsePowerObsessed]

I did not show a P0420 code until after the P0300 code was fixed and cleared, THEN i got the P0420 code. I cleared it and it came back about 10 minutes later.

[@tomkmetz6629]

Very informative

[@HorsePowerObsessed]

Happy to help!

[@KickingTires59]

Justin, did you know you don’t have to remove the plugs to find the bad one?

[@stephenr115]

Dude we are a family

[@HorsePowerObsessed]

100% 🤘

[@stephenr115]

Oh my on fuel pump

[@HorsePowerObsessed]

No reason for anything outside of the stock pump on a stock engine.

[@kerry_glock]

Good Stuff!

[@HorsePowerObsessed]

👍👍

[@chasehoover_14]

Is there a setting on the trx fog lights to stay on when turning?

[@HorsePowerObsessed]

You want them to stay on all the time or only when turning?

[@chasehoover_14]

@@HorsePowerObsessed stay on

[@HorsePowerObsessed]

@chasehoover_14 if you press the button to turn them on it will automatically disable them from only coming on when you turn the wheel

[@chasehoover_14]

@@HorsePowerObsessed if I have the fog lights on auto then I’m good or do I have to change anything?

[@HorsePowerObsessed]

@chasehoover_14 correct.

[@montrichardson8676]

I learned something new. I wonder if it would be good idea to test the new plugs before putting in the engine? It would avoid putting in a bad plug if it was a factory defect.

[@marklagasse2012]

Any news on cats or O2’s ?

[@HorsePowerObsessed]

Going in this upcoming week. Dealership said without looking at it, though it's very likely the catf failed after the spark plug issue. They've seen a similar issue in the past.

[@marklagasse2012]

Keep us updated

[@davidnclearlaketx]

Why wouldn't you number each plug as you removed it so you would know what cylinder It's associated with?

[@HorsePowerObsessed]

I probably should have but changing the plugs fixed the issue. As far as I was concerned there was no bigger reason to keep any of that in my head. One of the spark plugs was bad which caused the check engine light, once I replaced all the plugs the issue was gone. I didn't need to do any further research until some of my subscribers asked for it. I didn't really think it was going to be an issue and I actually had to pull the plugs out of the garbage because like I said, I thought I was done with them.

[@fanatic26]

Why on earth would that other guy change the coil and wires without ever changing the plugs?!? Some people dont deserve cars like the zr1

[@stephenr115]

Mark that puppy

[@v10tt]

Have you done any 60-130 and 100-150 on the ZR1 ? @horsepowerobsessed

[@HorsePowerObsessed]

Yes I have. Not on video though.

[@v10tt]

@@HorsePowerObsessedwhat did it run?

[@yeller95vette]

It’s an Electrode not Diode, thats a good job testing them.

[@HorsePowerObsessed]

Thanks. I'm not a professional by any means but I wanted to get as much info out there as possible about this spark plug failure.

[@yeller95vette]

@@HorsePowerObsessed​​⁠No worries, great videos!! Just trying to help!

[@HorsePowerObsessed]

Appreciate it! I’m always open to learning!

[@remnard1]

E3 plugs FTW

[@HorsePowerObsessed]

I prefer staying stock on this engine until modified.

[@stephenr115]

I get dealer or parts ets to sell another full set of plugs to someone not as smart as Justin

[@stephenr115]

Tape that damn thing down Justin sorry

[@HorsePowerObsessed]

lol I was about to!

[@MrPghs2kid]

Excellent! Great proof. Cant wait to hear what your buddy has to say about it 😂

[@m.g.maclaren3649]

The exact same thing happened to me and my C7. Bad plugs from the manufacturer?

[@HorsePowerObsessed]

There is a technical service bulletin out there from Chevy talking about bad plugs from factory so it’s very possible.

[@stephenr115]

Interesting. Just shows good research pays off!

[@thiosemicarbizidebenzoylal2921]

This excellent automotive problem solving. Kudos again for another sleuth finding on a C7 series car. Nobody else is doing this.

[@HorsePowerObsessed]

Thanks man. I knew it was the spark plugs but now I have proof that it was and honestly it feels good to know that for sure so I’m glad I went down this road.

[@stephenr115]

@@HorsePowerObsessed reportwe definitely need a final

[@remnard1]

Nice. Using a 4 dollar or free with purchase harbor freight vom. Buy a sperry or fluke.

[@HorsePowerObsessed]

Doesn't have to be anything fancy for this particular test. 👍👍

[@marct9360]

Unless you're doing high-end electronics work, a free Harbor Freight VOM works just fine.

[@HorsePowerObsessed]

💯

[@adamgriffin]

Get in the habit of changing spark plugs once a year for a healthy Gen V LT. Plugs are cheap and easy to change, there is no reason not to. Also Forums are the biggest source of disinformation. Bunch of guys afraid of voiding warranties arguing over oil weight.

[@vettesweetnos]

You do not need to change plugs every year, just get good ones and follow normal maintenance.

[@brianw8963]

@@vettesweetnos Exactly. If You need to change plugs once a year, you have a problem, to say the least.