Those of you who are running NGK BKR7EIX plugs, how often do you replace them? NGK says they should be good for 50,000 miles, but mine have 18,000 miles on them and the car has started having a stumble/misfire occasionally when under load. This was the same symptom that led me to replace my plugs a couple of years ago. I pulled the plugs recently and they don't have anything obviously wrong, but the stumble is definitely happening every now and then. I'm kind of thinking about going back to the NGK BKR7EQU and seeing how long they last.

 

I would just replace them. They aren't that expensive and my MINI too runs better with nice new plug so I replace them every year.

 

Check the plugs for arcing, I had a set that I installed and after about 5k miles, I started getting an intermittent miss, I thought "it couldn't be the plugs, I just changed them", chased it for over 6 months, it turned out that one of the plugs had two microcracks in the insulator, and it was arcing down the side of the plug- so check for arc tracks on your plugs.

 

I would also check the coil pack. The terminal at position: inside/drivers side, has a chronic history of corrosion while other three are pristine. If corroded use green side of a scrounge to clean it off. Nothing more abrasive than that.

 

I will have a look, but I have the MSD screamin demon coil (PO put it on and I've been too lazy to take it off) so I doubt the third terminal is rusty. It's easy to check for sure though. I replaced the plugs today and the stumble is gone so far. One plug (either 2nd or 3rd cylinder) had burn marks(?) some brown discoloration on the insulation above the hex part of the plug. Hopefully this was the problem.

 

Put the old coil pack back on... MSD is likely the problem. Mine was good for awhile then had the same symptoms you are having. Swapped plugs, nothing, swapped wires, nothing, swapped coil pack, all better. I usually change the plugs once a year, or about 30,000 miles.

Nik

 

Ugh, I might, last time I messed with the coil pack I managed to put a hole in the valve cover, hopefully I'm smarter now, but I'm a little scared to touch those bolts.

 

Also,
be sure to source your plugs from a reputable source and avoid ebay/amazon as there is a problem with counterfeit NGK's which look legit until close inspection.

I was almost burned by fake plugs somewhat recently:

https://www.northamericanmotoring.co...ml#post4546792

Sad but true.

 

Not something I'd heard of. I bought BKR7EQUP and put them in this weekend, but the stumble was still there. I had bought them off amazon, so I pulled one tonight to inspect it and see if it was counterfeit, but it looks legit.

So I faced my fears and removed the bolts for the coil and replaced it with the OEM coil that came off at about 50k miles. I took it for a spin and it was exactly the same. So for kicks I replaced the magnecor wires with the OEM wires that came off at the same time as the coil. (Thankfully the previous owner included the take offs with the sale of the car)

I took it for a spin with the OEM coil, OEM wires, and new NGK BKR7EQUP plugs and it pulled nice and smooth, no misfire, no stumble. So I'm guessing that the magnecor wires went bad, or maybe I didn't have the wires on good. I'm gonna stick with the setup I have now and see how it does, but hopefully it'll continue to be nice and smooth.