Hey Guys! Yesterday I had my car in the shop because I was having random misfires on acceleration or when the car got on boost. Turns out 2 of the brand new Bosch Iridium spark plugs I installed had failed catastrophically. The porcelain and the electrode are detached from the threads causing play but they have not fallen out. Note that I see both carbon fouling and oil fouling on one of the 2 failed plugs that I was given back. The other broken plug was disposed of. The misfire was caused by compression loss because the play in the plug was allowing the compression to leak out, and foul 2 of my coils. The coils are fine though. What could cause such a spontaneous failure like this? I definitely plan to negotiate a full refund from Autozone because this should not happen. I'll try and take some pictures of the plug once I'm finished with school.

 

A lot depends on which engine you have. Stock or mods? Could be the wrong plug --- lotsa mods want a colder plug. Also, NGK is usually the preferred brand --- OEM for many year /models. Could also be a bad AFR --- too lean or rich. We need more info ---

 

Did you do the install of the new plugs? First thought is maybe you did not use the correct plug. Second, maybe you asked for the correct plug but received the wrong ones. Third, you could have put pressure on the valve cover and influenced the gasket while replacing the plugs causing an oil leak from the valve train into the plug wells. Forth, maybe you did not torque to the correct spec, or if the engine was warm and the plugs were 10º like it was last week in Massachusetts, torque was incorrect.

At any rate, I would start by double checking the correct part was used. If so, replace them again and torque, bring to temp and re torque. I only do this when there is a significant temp delta between parts. Also, check your VC for leaks into the spark plug wells.

 

Spark plug failure is rare. To have two out of 4 fail is, well, extremely rare.

While the plugs could have been defective, my first thought when I read two plugs failed, is there is something "wrong", detonation maybe, going on that cause the plugs to fail like they did.

 

So I had these bosch Iridium plugs. My car had nothing done to it upon installing them to proper torque, and the only mod I have done is a ram air intake from DDMWorks as of now. When I did install the plugs though, my car had a random misfire which was caused by a bad coil. I did not know that the coil was bad at the time but it's been replaced now. When that coil went, the pre catalyst o2 sensor also failed too. Other than that, my car had been running perfectly fine until the spark plugs failed pretty marvelously.

 

When I get back from my christmas vacation, I will inspect the boxes from the plugs to see if they were wrong. I can guarantee though that they were partly the right ones because they needed a 12 point socket to be installed. Before buying them from Autozone, I did do my homework to make sure those bosch ones would work with my car.

 

One thing I will note is that it's been fairly icy around here when the failure happened, so maybe excess engine revving from slipping could have caused the failure? Honestly I really have no clue why this happened and the shop that discovered the two bad plugs, who are Mini specialists, were dumbfounded too.

 

I installed the plugs a month or 2 before the really windy 10º weather started setting in, so I don't think that could have caused any issues. I'm all ears for other ideas though

 

We've seen this several times and the most common cause it over torquing the plugs. But it also happens if the plugs are dropped as they are very thin and actually pretty fragile. You never know what happened to them before you got them in hand so it's hard to say if they are good until you install, but we do always recommend handling with care.

 

Sean Foody, If I were in your shoes, I would simply replace them with known good units and see what happens. It looks like you’ve done everything correctly. They may have been mishandled, over torqued, bad units from the factory... who knows.

 

Thank you for the advice. Fortunately the mini specialist replaced all 4 plugs with brand new ones which should hopefully last a bit longer, fingers crossed

 

When I installed them, I took great care to be gentle with them as I have overtorqued a spark plug on my go kart engine, where I broke the threads off of the plug, leaving them trapped in the hole. A bad experience definitely provides for some learning, but I appreciate the advice.

 

There are some fake spark plugs around as well. Inferior quality products, made to look like good brands.

it is particularily a problem with ngk, and most likely buying off ebay. But you never know ....

https://genuineisbest.com.au/counter...e-spark-plugs/

http://www.ngk-sparkplugs.jp/english...ake/index.html

 

I had a piece of the porcelain break off one of our plugs once as well. I think I ordered them from RockAuto. But like Way said, who knows how bumpy their ride to my house was. I just figured it was a fluke.

 

When I can I will take pictures of the spark plug and one of the boxes they came in. Either they're genuine or some impressive knockoffs because they look legit, but I'm not an expert after all. Who knows what to expect with Autozone nowadays.

 

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