Cylinder misfire!! P0304 - LOOK FOR THIS!!
 

Ok, so I recently acquired a 2000 Boxster S with 105,000 miles on it and very little in the way of maintenance records. I've posted some things on here in the way of whether or not I should do the IMS upgrade and replace the clutch but the cost is so high I wasn't sure if I wanted to do it at this time. The car was running fine with a few small issues I had to deal with until the other day it just all of a sudden started to run rough. the engine light came on and I checked the code to be a P0304 indicating cylinder 4 was misfiring or not firing. So, I jacked up the car after I got home and figured I would check the plug. This is what I found. The brand of spark plug was NRK-R or NRG-R or something like that....

The plugs in the car were the dual fire type. As you can see in the photograph, the center electrode had cracked inside the insulator and must have fallen into the cylinder. WOW! So, no wonder cylinder 4 was not firing. I placed a shop vac onto the hole where the spark plug boot/coil sits and tried to see if I could retrieve anything from the cylinder. My shop vac is very strong. No luck. I had the vacuum container empty but didn't see anything come through. Next, I placed a magnetic retrieval tool into the cylinder and tried to pull something out and I got a little bit of metallic grit. I mean, just about a 2 mm (millimeter) diameter amount of grit. It had attached to the magnetic tool tip but no electrode. I'm wondering if the electrode was ground up inside the cylinder. Any thoughts?

Finally, I used another flexible magnetic retrieval tool and rotated it around as much as I could but still no dice. Nothing out of there except for a little more of that grit. I found a left over bicycle spoke I had laying around the garage and slid it into the spark plug where the electrode was missing. It went in around 3/8" so I'm guessing that's how much electrode was broken up and ground up.

After cleaning out the cylinder with the magnet and shop vac as much as possible, I replaced the spark plug and started it up again (I know, why would I do this right?). Well, the car ran like a top again. I replaced all 6 plugs and inspected them. All cylinder plugs (including #4 - with the exception of the missing electrode) appeared to be firing well. No signs of oil burning or running too lean or anything.

I just thought I would see what you guys thought about this and figured I would post it to the forum so you guys could check for this if you have a misfire code. I would recommend staying away from this brand of plug and actually this type of plug. I've never had this happen before and am not sure how common it is. However, I bought the plain old school type of plug in a platinum line and will stick with those for now on. That way, if the electrode cracks in the insulation, at least the other conductor that is bent over the electrode will prevent it from just falling out and causing scratches and damage to the cylinder. Something to think about....

Please reply with any comments. I'd appreciate hearing what you guys think.
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Good info, thanks for posting that. Hopefully the remainder of that electrode has been kicked out with the exhaust.
You can get a very inexpensive USB inspection camera and poke it in the hole if you want to inspect it further.

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Interesting (and worrisome) story, but as the basis of it is the brand and type of plug, it would be more helpful if you could tell us what the plug is. Probably NGK R. Which I run... :(

Yes. NGK-R

I would replace them.

Thanks for the info on the inspection cams. I thought about that but I couldnt find a Milwaukee M12 Inspection Camera anywhere in stock and got impatient. The ones you posted look like a great price. I'm definitely gonna give one of those a shot. Have you used any of those before? If so, how good was the resolution? I'm pretty sure I either vacuumed it out or it shot out with the exhaust. some of it probably broke up in the cylinder but I think I pulled that out with the magnet. I also failed to mention that my cylinder was making a "ticking" sound like the valve was out of adjustment but it is completely gone now and the car runs like a top again!! Maybe I will check cylinder compression when I have nothing else to do to see if it is any lower than the others now,....but that will be a while. Now its time to hunt down where my slow oil leak is coming from. It's definitely higher up on the motor. I'll have to take some pics and post that job as well.

Nothing wrong with NGK as a brand, as they are the largest spark plug manufacturer to OEMs in the world. Had those in my Volkswagens and had no issues. That said, I used Beru plugs when I replaced mine in the '04 just recently (and turns out that's what was already in there).

Sounds like it was an eventual fault in that particular plug that allowed the electrode to separate.

Given 21st century ignition system technology there's simply nothing to be gained in changing type of sparkplug. OE and OE equivalents are it.