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Discussion Starter · #1 ·
Checked my plugs today still searching for the stumble I've been getting at WOT and found this... the one on the left is representative of the other two plugs. The one on the right is missing the tip. Obviously, I'm going to change the plugs but what does it mean and should I be worried? Also, would this cause an engine stumble at WOT?



Thanks,
Matt
 

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Discussion Starter · #2 ·
Checked my plugs today still searching for the stumble I've been getting at WOT and found this... the one on the left is representative of the other two plugs. The one on the right is missing the tip. Obviously, I'm going to change the plugs but what does it mean and should I be worried? Also, would this cause an engine stumble at WOT?



Thanks,
Matt
Anyone?
 

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Could absolutely be the cause of your stumble problem--extremely large gap there :eek:.

As for why--it could be a quality problem with the plug or some kind of voltage spike being delivered to it by the ignition system. Whatever the case, you should keep a eye on it--checking maybe every 1K miles, or so.
 

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Could just be a random failure because the tip wasn't welded properly, but it might have been caused by detonation. If the plugs don't show any other signs of detonation it's probably just a random failure.
 

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What kind of plugs are these? Platinum? Iridium? My guess would be the tip broke or melted off since the others aren't worn down as far. Probably didn't cause any damage, but it could be embedded in the top of the piston. Even this probably won't cause any issues as I've seen much worse stuff embedded in pistons and the engines ran fine. I've even seen pluges where the entire ceramic area has fallen apart and there was no damage to the engine.

This could also very possibly cause your higher RPM problem, especially if your running boost... As boost / cylinder compression increases it takes more energy to jump the spark. Since the gap is increased it's possible that it's finding too much resistance and not lighting off when under boost at the higher RPM's...
 

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Discussion Starter · #6 ·
What kind of plugs are these? Platinum? Iridium? My guess would be the tip broke or melted off since the others aren't worn down as far. Probably didn't cause any damage, but it could be embedded in the top of the piston. Even this probably won't cause any issues as I've seen much worse stuff embedded in pistons and the engines ran fine. I've even seen pluges where the entire ceramic area has fallen apart and there was no damage to the engine.

This could also very possibly cause your higher RPM problem, especially if your running boost... As boost / cylinder compression increases it takes more energy to jump the spark. Since the gap is increased it's possible that it's finding too much resistance and not lighting off when under boost at the higher RPM's...

Thanks for the info, guys... Like you Dragon, I have the BWR so these plugs are the NGK iridiums that come with the kit. I'm replacing the plugs ASAP and will report back to let let you know if it resolves my stumble issue.

Thanks!

Matt
 

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Thanks for the info, guys... Like you Dragon, I have the BWR so these plugs are the NGK iridiums that come with the kit. I'm replacing the plugs ASAP and will report back to let let you know if it resolves my stumble issue.

Thanks!

Matt
Cool.. Hope the new plugs fixes your issue.. Also since the BWR tune is a little rich on the top end for safety it would further increase the chances of miss fire with the bad plug..

Also be sure to post the results when your done.. I hate threads with no conclusion.. :D
 

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make sure they are gapped properly before installing them. Have found many times that plugs are not gapped properly from the factory.
 

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Discussion Starter · #9 ·
Cool.. Hope the new plugs fixes your issue.. Also since the BWR tune is a little rich on the top end for safety it would further increase the chances of miss fire with the bad plug..

Also be sure to post the results when your done.. I hate threads with no conclusion.. :D
Obviously I do not want to count my chickens before they hatch but after changing the plugs and taking a quick spin around the block, I had no stumble at WOT. I'll post back once I've had a chance to drive the car a bit and really confirm the issue it resolved. Thanks for the info guys! I'm really hoping that I've isolated and solved the issue!

Matt
 

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Matt,

A few questions -
1) Does your engine have forced induction?
2) How many miles on the plugs?
3) What are your driving habits? Track Days?

It appears that the electrode is "melted" or "worn". Typically this is caused by high heat which is a product of higher pressures (forced induction) and/or lean air-fuel mixture.

And, absolutely this would cause a misfire at higher RPMs.

Cheers,
Kiyoshi
 

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Discussion Starter · #11 ·
Matt,

A few questions -
1) Does your engine have forced induction?
2) How many miles on the plugs?
3) What are your driving habits? Track Days?

It appears that the electrode is "melted" or "worn". Typically this is caused by high heat which is a product of higher pressures (forced induction) and/or lean air-fuel mixture.

And, absolutely this would cause a misfire at higher RPMs.

Cheers,
Kiyoshi
1. Yes I have the BWR supercharger with Charlie's tune.
2. Around 2000 miles on the plugs (and supercharger install) but problem started about 1000 miles ago following a larini sport exhaust "failure." The morning it all started I threw a lean code. The code has not returned.
3. No track days or abuse. Occasionally I take a canyon run or a quick acceleration in a long straightaway but no heavy duty wear and tear.

Thanks,
Matt
 

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1. Yes I have the BWR supercharger with Charlie's tune.
2. Around 2000 miles on the plugs (and supercharger install) but problem started about 1000 miles ago following a larini sport exhaust "failure." The morning it all started I threw a lean code. The code has not returned.
3. No track days or abuse. Occasionally I take a canyon run or a quick acceleration in a long straightaway but no heavy duty wear and tear.

Thanks,
Matt
Oops forgot to include ignition timing, adds to higher cylinder temps.

Nothing unusual to suspect your driving. It could have been a bad plug, so watch the new set closely.

But, the old melted one shows all the signs of high cylinder temps which are typically caused by boost, lean mixture and/or advanced ignition timing. (edit - "melt" not in the literal sense, but accelerated wear due to high temps)

Kiyoshi
 

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Discussion Starter · #13 ·
Oops forgot to include ignition timing, adds to higher cylinder temps.

Nothing unusual to suspect your driving. It could have been a bad plug, so watch the new set closely.

But, the old melted one shows all the signs of high cylinder temps which are typically caused by boost, lean mixture and/or advanced ignition timing.

Kiyoshi
Thanks for the heads up. I'm going to pull the plugs in 500 miles or so to check them out. It was the 1st plug on the driver's side if that makes a difference.

Matt
 

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As there are no other signs of melt on the plug, I'd tend to rule out detonation. What octane fuel were you running, and how hot has it been in your area?

Looks like the tip just separated. They're virtually impossible to melt. Might not be a bad idea to take a look in the cylinder and make sure the tip isn't bouncing around in there. You may also get lucky with a small strong magnet on a string.

Try the Denso Iridium plugs. Much higher quality IMO (and reflected in the price).
 

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As there are no other signs of melt on the plug, I'd tend to rule out detonation. What octane fuel were you running, and how hot has it been in your area?

Looks like the tip just separated. They're virtually impossible to melt. Might not be a bad idea to take a look in the cylinder and make sure the tip isn't bouncing around in there. You may also get lucky with a small strong magnet on a string.

Try the Denso Iridium plugs. Much higher quality IMO (and reflected in the price).
:panic: NO Magnet on string... lol.. It'll drop in and stick to the cylinder wall or valve and may not come back out... I have a friend who did that... :wallbang:

I don't think iridium is magnetic anyway, but I could be mistaken.
 

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:panic: NO Magnet on string... lol.. It'll drop in and stick to the cylinder wall or valve and may not come back out... I have a friend who did that... :wallbang:
It will if you make it properly, and is relatively safe as the nikasil in the bore isn't very magnetic. The valves are somewhat more an issue, but a magnet small enough to fit in the plug hole will pop off of them easily. Done it several times.

I don't think iridium is magnetic anyway, but I could be mistaken.
Iridium isn't, however the "iridium" used on spark plugs is an alloy, which is slightly magnetic and will generally stick to a powerful neodymium magnet.
 

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Did you install colder plugs with your BWR install?
 

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Discussion Starter · #18 ·
Did you install colder plugs with your BWR install?
Yes, I replaced the plugs when I installed the supercharger... I can remember but I think they came with the kit or at the very least, I bought what was suggested...

As far as octane is concerned... we only have 91 here in Kalifornia aside from race gas which is getting hard to find at a pump.

I have a telescoping magnet tool... wouldn't that get into the area in question?
 

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Yes, I replaced the plugs when I installed the supercharger... I can remember but I think they came with the kit or at the very least, I bought what was suggested...
FWIW, the recommended plugs for a forced induction motor (SC) are NGK Iridium BKR7EIX-11. or the NGK Standard (V-Power) BKR7E-11.

These are 1 range colder than the stock plugs. (7 versus 6).

My BWR kit did NOT come with the plugs, so I bought them locally.

Regards,
Wayne
 
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