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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > NA Engine (non-turbo) / Drivetrain / Exhaust Modifications > Spark Plug Replacement Spec Change



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      11-19-2019, 06:42 AM   #1
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Spark Plug Replacement Spec Change

So just an interesting question to ponder...

In my 2006 325i, last week I just did some long needed tune up maintenance, which included a CCV replacement. Just a month ago the engine developed a drivability issue. It would instantly drop power, it felt like the clutch would slip just for an instant, only at low RPM high-load situations. Being the clutch/pressure plate/flywheel is rather fresh since I replaced all of it at 293,000 miles it only has 100,000 on it, so my thoughts when to did I reassemble everything correctly. Being I was soon to replace the CCV, I decided to wait for further diagnosis of the drivability issue. Mind you, no illumination of the SES light surfaced.

With the CCV replaced and the engine running better, the instant power drop was less prevalent but strangely moved up in RPM range. I decided to pull codes. Sure enough, there was a misfire code. I knew the plugs were almost due; I replaced them 95,000 miles ago when I lost coil No. 5 and replaced the rack of coils and plugs in August 2015.

Over to my N52-powered Z4. It just hit 100,000 miles the same week I was working on the E90, so it's plugs were due. The Z4 was running perfectly.

So that got me to thinking. For 2010 model year N52 E9X, BMW dropped the plug replacement interval from 100,000 miles to 60,000 miles. When I pulled the plugs on the E90 I checked the spent plugs gaps. The plugs were Bosch that I sourced from BMW in 2015. The gap spec is .044". The plugs that came out were at .055 - .060, which I thought was unusual; I mean they were visually wider in gap than what I remember the plugs that came out at 287,000 miles, or even at 99,000 when I pulled the factory set out.

I replaced the Z4 plugs the same day. The plugs were the factory installed set and were NGK. The gaps were a bit off from the factory .040" setting.

So I wonder if when BMW dropped the change mileage spec, it also revised the spark plug spec so that current plug designs for the N52 are no longer 100,000-mile spark plugs.

Thoughts?
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      11-19-2019, 09:01 AM   #2
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I swapped mine out at about 45k interval. I thought I was crazy too when I saw the gap on the first set I took out (Bosh). Like you, plugs were spent at 45k miles. Gap was about 48 on average. Second set were ngk. After 50k they looked in very good shape. However, gap was still bit bigger than specs - ranged from 44-46. Leads me to believe that bosh plugs wear faster than ngk and maybe thatís why bmw decided to reduce the recommended interval.
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      11-20-2019, 01:23 AM   #3
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11/2010 Build 328i. Bought with 57,400 miles.

Had my first misfire at 59k miles. Pulled the plugs (NGK 11GS) at 60k miles and found all the plugs at 0.54-56. Installed new NGK plugs AND AT 68k miles the misfire returned. I figured a coil was weak from the stress of such a large plug gas 8k miles prior. I pulled all the coils, regaped the plugs, and swapped in ALL new Delphi Coils from FCP.

At about 78k miles I started my car up after running an errand on the weekend and it started misfiring horribly. I limped it home and pulled the #4 plug that had some visible oil in the well. The plug has almost no electrode on it anymore. Bought one plug and threw in an original Bosch coil and was on my way.

At around 85k miles the misfire returned. I decided to do a 3 stage manifold swap and a valvetronic motor gasket to stop the oil dripping into the #4 plug well and swap back in a new Delphi coil from FCP. FCP Actually screwed up the order and sent me 6 total coils, not just the one I ordered and was charged for.

Pulled the valve cover off and saw no oil in the #4 well, plug gap was still 0.44. Decided pull the remaining 5 plugs and found them at 0.54-56 again this time with only 25k miles on them.

So then I decided to go get 5 new plugs and install 6 new Delphi coils and WOW!!! The car had never run better in almost 30k miles of ownership.

I'm now at 91,500 miles and the car runs so great I've finally fallen in love with it.
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      11-20-2019, 08:32 AM   #4
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Interesting.

I had a misfire in cylinder #3 on my E90 with the N51 at 40k miles or so. It ended up being a bad coil (swapped the coil and the issue followed the coil) but I also replaced the plugs at the same time, and they were smoked.

I've read the N51 is harder on plugs for some reason. Not sure if that is true, but mine were definitely due by 40k miles and were factory OE. Meanwhile I did the plugs in a friend's 2006 N52 and at 130k miles they still looked decent.
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      11-20-2019, 12:53 PM   #5
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Quote:
Originally Posted by CTinline-six View Post
Interesting.

I had a misfire in cylinder #3 on my E90 with the N51 at 40k miles or so. It ended up being a bad coil (swapped the coil and the issue followed the coil) but I also replaced the plugs at the same time, and they were smoked.

I've read the N51 is harder on plugs for some reason. Not sure if that is true, but mine were definitely due by 40k miles and were factory OE. Meanwhile I did the plugs in a friend's 2006 N52 and at 130k miles they still looked decent.
Changed the plugs on my sisters 95k mile 2006 Z4 last year and they weren't bad, but she had a slightly rough idle. New plugs improved the idle and smoothness.
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      11-21-2019, 06:34 AM   #6
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Quote:
Originally Posted by W37V View Post
I swapped mine out at about 45k interval. I thought I was crazy too when I saw the gap on the first set I took out (Bosh). Like you, plugs were spent at 45k miles. Gap was about 48 on average. Second set were ngk. After 50k they looked in very good shape. However, gap was still bit bigger than specs - ranged from 44-46. Leads me to believe that bosh plugs wear faster than ngk and maybe thatís why bmw decided to reduce the recommended interval.
So that's really the question, are the new versions of the N52 spark plugs still 100,000-mile plugs.

I replaced the plugs in the E90 at 98,939 in December 2009. The second replacement (3rd set of plugs) went in at 195,570. None of these three sets of plugs, the factory set and my two replacements, had any hint of drivability issues. The third replacement set went in at 287,585, a bit early due to losing the coil on cylinder#5, which brought up an SES light and misfire codes. While none of those replacement intervals was exactly 100,000 miles, they all were 30,000+ miles beyond the 2010 MY spec change.

The Z4 I bought used at just 23,000 miles. I have the service records from BMW and Carfax. No plug change was indicated so I 99.999% sure the plugs I just replaced at 100,300 miles were the factory set. The Z4 was running perfectly at the time I changed the plugs last weekend.
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      11-22-2019, 10:17 PM   #7
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Quote:
Originally Posted by Efthreeoh View Post
So that's really the question, are the new versions of the N52 spark plugs still 100,000-mile plugs.

I replaced the plugs in the E90 at 98,939 in December 2009. The second replacement (3rd set of plugs) went in at 195,570. None of these three sets of plugs, the factory set and my two replacements, had any hint of drivability issues. The third replacement set went in at 287,585, a bit early due to losing the coil on cylinder#5, which brought up an SES light and misfire codes. While none of those replacement intervals was exactly 100,000 miles, they all were 30,000+ miles beyond the 2010 MY spec change.

The Z4 I bought used at just 23,000 miles. I have the service records from BMW and Carfax. No plug change was indicated so I 99.999% sure the plugs I just replaced at 100,300 miles were the factory set. The Z4 was running perfectly at the time I changed the plugs last weekend.
That is most likely. I mean, people like to shit on bmw, but bmw engineers are not idiots. If they originally expected plugs to last 100k, Iím sure they can, but most likely plugs might cause some issues towards end of their lifecycle. Then again, maybe the initial number was set by some marketing guy who wanted to compete with Honda, who ďconvertedĒ 100k km into 100k miles.

But... did you notice any power gain after swapping them?

In my case, I didnít have drivability issues either. Granted, mine were at 50k and my car has been running a tune for over 50k miles now. Swapping out plugs resulted in much smoother engine operation over entire rev range.i think I may have restored quite few hp. Fuel economy remained the same thou.
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      11-23-2019, 05:55 AM   #8
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Quote:
Originally Posted by W37V View Post
That is most likely. I mean, people like to shit on bmw, but bmw engineers are not idiots. If they originally expected plugs to last 100k, I’m sure they can, but most likely plugs might cause some issues towards end of their lifecycle. Then again, maybe the initial number was set by some marketing guy who wanted to compete with Honda, who “converted” 100k km into 100k miles.

But... did you notice any power gain after swapping them?

In my case, I didn’t have drivability issues either. Granted, mine were at 50k and my car has been running a tune for over 50k miles now. Swapping out plugs resulted in much smoother engine operation over entire rev range.i think I may have restored quite few hp. Fuel economy remained the same thou.
To me it always seems the engine runs better once the new plugs have seasoned a bit. Much like the phenomenon that people think the engine runs better after an oil change with fresh oil in it. My engineering background tells me different.

This is the first time in the history of my E90 that it has developed a misfire with the plugs at or near the 100,000-mile replacement interval. It could be a factor of the engine's age combined with a bit more engine oil being in the fuel mix as a result of a aged and failing CCV system. The only other time the engine has recorded a misfire was when the No. 5 coil died at 287K, but that immediately threw a SES light.
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A manual transmission can be set to "comfort", "sport", and "track" modes simply by the technique and speed at which you shift it; it doesn't need "modes", modes are for manumatics that try to behave like a real 3-pedal manual transmission. If you can money-shift it, it's a manual transmission.

Last edited by Efthreeoh; 11-25-2019 at 06:26 AM..
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      11-25-2019, 01:20 AM   #9
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Interesting stuff. 2 data points on my end for plugs.

I just did the 100k plug change on my 2009 E91. The plugs that came out were the NGKs. Oddly, and rather shockingly, they were all dead on at .040". They also worked perfectly.

I put in the Bosch OE part #. No change in how the car runs despite cylinder #4 plug well being 1/4 full of oil (to be continued I'm sure...). Hopefully, the Bosch plugs are 100k mile spec?

On a family member's 2011 N51 car I replaced the plugs and 2 coils thus far. At about 50k miles. Missfire issues twice with that car.

Efthreeoh How's the oil consumption now with the new CCV?
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      11-25-2019, 06:20 AM   #10
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Quote:
Originally Posted by tlow98 View Post
Interesting stuff. 2 data points on my end for plugs.

I just did the 100k plug change on my 2009 E91. The plugs that came out were the NGKs. Oddly, and rather shockingly, they were all dead on at .040". They also worked perfectly.

I put in the Bosch OE part #. No change in how the car runs despite cylinder #4 plug well being 1/4 full of oil (to be continued I'm sure...). Hopefully, the Bosch plugs are 100k mile spec?

On a family member's 2011 N51 car I replaced the plugs and 2 coils thus far. At about 50k miles. Missfire issues twice with that car.

Efthreeoh How's the oil consumption now with the new CCV?
Thanks for asking.

So as of Wednesday last week the e-dipstick reported a 1/4-quart low. I have to check my notes in the car, but I think I had about 500 miles on the topped off oil level (i.e. 500 miles under the "old" consumption rate) when I installed the new CCV at 383,056 miles. I changed the oil last at 378,797 in August and added 2 liters over the 4,200 miles since the oil change. I think I'm at now at 383,970 or so, so that's 1,300 miles to take the level to drop 1/4 quart, which is a vast improvement, since the last consumption readings were a full quart about every 1,800 - 2,200 miles. I'll let the engine get to the +1 notification and then top off again, and then get some real data without estimates in it. And keep in mind when I say quarts I mean liters since I use BMW oil and it is sold by the liter now.

But I think the oil consumption rate has improved from what I can tell so far. I also replaced the engine air filter as of yesterday. That may help. The oil level sensor seal is weeping oil now, not much, it just makes the bottom of the oil pan wet, so I'm losing a teeny bit of oil there.

I'm driving the E90 today, so I'll true up the numbers when I get the real info out of my log book.

And yup, I think the NGK plugs lose less of a gap than the Bosch. So funny thing is, when I changed the plugs in the Z4 and E90 just a few weeks ago, Bosch came out of the E90 and I installed NGKs. NGKs came out of the Z4 and I put in Bosch. I bought the 12 plugs all in the same day, but one store only had 6 NGKs and the other store only had 6 Bosch. In a few years I hope I'll remember I posted this thread and report back.
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A manual transmission can be set to "comfort", "sport", and "track" modes simply by the technique and speed at which you shift it; it doesn't need "modes", modes are for manumatics that try to behave like a real 3-pedal manual transmission. If you can money-shift it, it's a manual transmission.

Last edited by Efthreeoh; 11-26-2019 at 06:25 AM.. Reason: added real numbers
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      11-27-2019, 03:46 PM   #11
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Quote:
Originally Posted by tlow98 View Post
Interesting stuff. 2 data points on my end for plugs.

I just did the 100k plug change on my 2009 E91. The plugs that came out were the NGKs. Oddly, and rather shockingly, they were all dead on at .040". They also worked perfectly.

I put in the Bosch OE part #. No change in how the car runs despite cylinder #4 plug well being 1/4 full of oil (to be continued I'm sure...). Hopefully, the Bosch plugs are 100k mile spec?

On a family member's 2011 N51 car I replaced the plugs and 2 coils thus far. At about 50k miles. Missfire issues twice with that car.

Efthreeoh How's the oil consumption now with the new CCV?
Spoke too soon about the E91 - woke up this morning to rumble-y N52 with CEL illuminated.

Throwing 29D0 code. Missfire cylinder #4. Shocker. Bad timing as we need the car with family in town, so I went to Autozone. $70 after tax for one coil! ugh. The same part on Rockauto is only $18.

Oh well, need it to be operational. Not exactly sure it's the issue, but will likely know tonight.
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      11-28-2019, 08:00 AM   #12
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Quote:
Originally Posted by tlow98 View Post
Spoke too soon about the E91 - woke up this morning to rumble-y N52 with CEL illuminated.

Throwing 29D0 code. Missfire cylinder #4. Shocker. Bad timing as we need the car with family in town, so I went to Autozone. $70 after tax for one coil! ugh. The same part on Rockauto is only $18.

Oh well, need it to be operational. Not exactly sure it's the issue, but will likely know tonight.
Zeit ist geld; time is money, my friend. Who knows the quality of Rock Auto parts anyway.
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      12-02-2019, 11:54 PM   #13
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Originally Posted by Efthreeoh View Post
Zeit ist geld; time is money, my friend. Who knows the quality of Rock Auto parts anyway.
All true.

It was the coil pack. More oil in the plug well. Ordering parts for the VCG.

First time - yay! Intend to reuse the VC itself, barring any cracks or PCV vslve failures.
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