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E46 Spark Plug DIY

142451 Views 42 Replies 32 Participants Last post by  rbelton
I changed my spark plugs last weekend and I thought I would document it for the benefit of other less mechanically experienced board members like myself but who know just the basics.

My car is an E46 2001 325i. Spark plugs used : BMW OEM (NGK BKR6EQUP).
Tools needed: T30 Torx bit screwdriver, flat head screwdriver, ratchet, 10mm socket, 6" extension bar, 5/8" spark plug socket.

Step 1
Open the cabin microfilter cover and remove the microfilter. Unscrew the 4 Torx screws (T30) highlighted, in the microfilter housing. Carefully snap off the 4 clips holding the 2 cables in the front of the housing. Ease out the 2 cables from the clips. Lift off the microfilter housing.


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There is no bigger/better spark or more complete combustion, if there was the MFG would be all over it since more complete combustion would gain lower emissions, more HP and huge tax advantages for pennies per car, it either sparks or it doesn't, no science or data at all to support that 4 prongs are better than 1,2, or 3.

Not to thread crap but its just bad info that gets past around a lot. Kind of like vented/slotted rotors ( with less braking area thus less friction material and correspondingly less braking efficiency) will somehow give better performance. They dont, never have, never will. Its a simple equation, how much surface area do the pads have to contact, take any away and the performance goes down.

One of the biggest waste of your DIY dollars and potentially the easiest to cause significant engine damage is using a plug other than that of the MFG's specs. The best part is the NGK OEM's are a few bucks each. People spend the price of a set of 6 OEM plugs for ONE Iridium or 4 prong or the latest rage plug, ask a mechanic, one you trust, dont take my word for it, he will tell you its snake oil.

Please dont think I'm calling anyone a liar or dumb, there is a lot of misinformation out there and this is something I know quite a bit about. Changing your plugs at 50K BTU is overkill, wasted money, if you can live with that then go ahead., but dont expect any tangible benefit, because you will not get any. You will one day, when the car wont start and after changing the failed plug /plugs then you will see the benefit, no sooner.

Its like a light bulb, it works or it doesn't, there is no in between:eeps:
I noticed that too. I assume it allows for a bigger spark which give a more complete combustion of the fuel mixture.
Ideally prior to that. I would think any competent technician or DIY'r would see the lunacy of changing plugs at 10K intervals. Unless you had serious engine work, track the car, a lot...., or in the case of Pelican, sell plugs.

Take it for what its worth, its a cheap part of any maintenance regime, but it does come with a cost, a risk whatever you call it. If you have never installed a Helicoil insert into threaded head, I would use the money elsewhere.

That's just me, I have been wrong before, ask my ex....
so are you saying you only replace your spark plugs when your engine won't start?

On Pelican's DIY page they say to replace every 10k which I think is excessive, but you're on the other end of the spectrum. I generally trust Pelican, though.
Key thing is what is making the misfire? Plugs are rarely the cause. I would guess a coil for the cost and ease of swapping the coil to another cylinder and seeing if the fault follows the coil, why not give that a try first?
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