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2Addicts | BMW 2-Series forum Technical Topics N55 (M235i) Engine, Transmission, Exhaust, Tuning Misfiring after spark plug change - help me!

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      05-11-2019, 05:59 PM   #1
stevemg9
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Misfiring after spark plug change - help me!

Back to the forums with some issues on my ‘14 M235i. After BMW telling me I needed new spark plugs and that it would be $650, I thought pshh that’s an easy job, I’ll just do it myself. Alas, Murphy’s law is real, and now I’m misfiring on cylinders 5 and 6. I pulled the plugs from those cylinders checked them for any damage, put them back in, reseated the coil packs and inspected the wires, couldn’t find anything wrong. Thought maybe it was the plugs so then I put all the old ones back in (all 6 cylinders) still misfiring. I cleared the codes and now it’s not throwing codes anymore, but I’m afraid to drive it long enough to throw new codes because it’s running like crap, hesitating and sputtering all over the place. Any thoughts on what this could be? My guess is a coil pack or wiring issue. The car is stock except for a fabspeed sport cat.

Also I bought the plugs on rock auto. They’re the Bosch plugs with the same exact model number as the OEM ones but they don’t have the BMW logo. Either way I don’t think that’s the issue because I have the OEM ones back in now and it’s still misfiring.
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      05-12-2019, 11:58 AM   #2
drodrig2
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A simple cheap trick you can do today is Move your #5 and #6 coil and/or plugs to the #1 and #2 cylinders. If you get miss fire code on cylinder 1 or 2 then you will know it is a bad coil and/or plug and can replacement them accordingly. Also you can check the gaping of the new spark plugs to make sure they are correct.

Last edited by drodrig2; 05-12-2019 at 12:58 PM..
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      05-12-2019, 01:51 PM   #3
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Make sure the coil connectors are in completely, mine were a pain to get back in perfectly. The latch will pull the connector in and latch down even if it's not lined up correctly, I had 2-3 dead cylinders when I did mine recently, ended up just being the connectors.

Last edited by jb-slow; 05-15-2019 at 07:25 PM..
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      05-12-2019, 06:53 PM   #4
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Quote:
Originally Posted by jb-slow View Post
Make sure the coil connectors are in completely, mine were a pain to get back in perfectly. The latch will pull the connector in and latch down even if it's it's not lined up correctly, I had 2-3 dead cylinders when I did mine recently, ended up just being the connectors.
So the car was running pretty bad yesterday, I unhooked all of the wires from the coil packs and reseated them being very careful to make sure it was locked in. I took it out and it was running fine for a few minutes and then started misfiring once I put it in sport+ and gave it some real throttle. So it seemed like it was running on all cylinders for a few minutes before it started misfiring. It threw codes for misfires on cylinders 2, 3, 4, and 5 this time. I think it has to be the wires. Is there any way to lock them in besides the plastic clips? Maybe they’re coming loose from vibrations over time? I should note that when I test drove it, I did not have the engine cover or the NVH foam back in there simply because I didn’t want to keep putting it in and pulling it out.

Also what do you mean by “get back in perfectly”? It’s like a triangular connector that only seems to be able to go in one way. I don’t know how else I could be messing it up.

Last edited by stevemg9; 05-12-2019 at 06:56 PM.. Reason: Additional question
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      05-14-2019, 11:23 AM   #5
XutvJet
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Are you sure you have the coils plugged into the correct spark plugs?

Have you checked the plug gaps?

Are you sure they're the Bosch ZR5TPP33S plugs?

Are the plugs torqued to spec which is 17 ft/lbs? Remember, the new plugs have new crush washers so torquing them correctly is critical to get the washer to crush.

Did you have to pull hard, tug, etc. to get something out when removing any electrical parts?
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      05-15-2019, 06:41 PM   #6
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Quote:
Originally Posted by XutvJet View Post
Are you sure you have the coils plugged into the correct spark plugs?

Have you checked the plug gaps?

Are you sure they're the Bosch ZR5TPP33S plugs?

Are the plugs torqued to spec which is 17 ft/lbs? Remember, the new plugs have new crush washers so torquing them correctly is critical to get the washer to crush.

Did you have to pull hard, tug, etc. to get something out when removing any electrical parts?

Plugs were all gapped right around 0.027 and they were the exact same model number as the OEM plugs just didn’t say “BMW” on them.

Torqued them all to 17 ft.-lbs

I don’t recall forcing or pulling anything. Didn’t disconnect anything electrical besides the battery and the coil packs.

Talked to some shops and they said first guess would be the coil packs. Just ordered 6 new coil packs and put them on and it’s still misfiring so I’m at a complete loss. I inspected every visible wire and connector in the engine bay and I’ve got nothing. My only guess is that is that it’s a wiring or air/vacuum issue. I’m officially out of my depth now so it’s going to the shop tomorrow. I really just want to know what the hell I did wrong at this point...
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      05-16-2019, 09:35 AM   #7
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Alright, after having my car towed to a local independent shop - they said they can't find anything wrong with it. The mechanic said he thinks the spark plug change was likely a coincidence and that he thinks it's a carbon buildup on the valves that is causing the issue. He said only BMW has the tool to clean them (walnut blaster).

Now here is my issue, the car is still under the CPO warranty so I would think the valve cleaning would be covered under warranty. The new spark plugs and coil packs match the original part numbers but they are not "Genuine BMW" parts. If I take the car in with the new plugs and coil packs I'm worried that they are going to try to tell me that I did something wrong putting them and not cover whatever needs to be done under warranty or they are just going to tell me that the plugs and coils need to be changed out with "Genuine BMW" parts before they do anything else - and I don't want to pay for 2 sets of plugs and coils.

Also, I have a Fabspeed SportCat on there which I'm assuming I'll have to take off? What happens if I don't? Would they really look under there? The car has been running perfectly for almost a year with the FabSpeed cat on there and I really don't think this is an issue related to that part.

Do I really need to return the car to stock for this? Including spark plugs and coil packs? Just the cat?

Any thoughts or opinions would be very helpful!
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      05-16-2019, 10:32 AM   #8
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In my experience the dealer will use any aftermarket part you have installed as a excuse to void warranty or to blame your problem on it. Unless you know a service rep well and he is on your side.. I would return the car to stock for warranty work.
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      05-16-2019, 11:19 AM   #9
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+1, don't give dealership any reason to weasel there way out of warranty work.
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      05-16-2019, 01:00 PM   #10
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I have a hard time believing the car has carbon build up. The N55s really don't have a carbon build up issue and only need servicing every 80-100K miles. The N54 motors have major issues with build up and need walnut blasting every 30K miles or so.

Since you've swapped in the old plugs and new coils and the issue is still there, I'm just as dumbfounded as you now.

When doing the spark plugs, did you unplug the battery? If you didn't unplug the battery, I wonder if a short was created somewhere when something was removed or grounds touched

Perhaps disconnect the battery now, let it sit for a few minutes, reconnect, and see what happens?

If that doesn't do it, I'd do the following and be annoyed as hell doing it:

1) Disconnect the battery
2) Put the old plugs in
2) Put the old coils in
3) Reinstall the OEM cat
4) Reconnect the battery
5) Go to BMW and play dumb

The car needs to be put on a professional level scanner to watch the sensors/inputs and pinpoint the issue.
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      05-22-2019, 03:55 PM   #11
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Thanks for the input guys. I had the indy shop swap the original cat back in. Good news is they only charged me $50, bad news is they never hooked up the oxygen sensor - guess you get what you pay for. After the terrible 1.5 mile drive home in limp mode, I swapped back in the original spark plugs and coil packs - that's when I noticed the connector for the O2 sensor was just hanging loose. Started it up one last time and had some hard codes for misfires on 5 cylinders and and a oxygen sensor fault.

BMW told me that i needed new spark plugs and that "all of the ignition coils were exhausted." They also tested the O2 sensor and said it was faulty and needed to be replaced. I'm not sure if that code was thrown because I drove the car for a mile and a half without the sensor plugged in or because the sensor actually was faulty and I just hadn't driven it long enough to get that code before.

Either way, new plugs, coils, and an O2 sensor installed by BMW seemed to fix everything. The coils and O2 sensor were covered under CPO warranty so that was a relief. I wish I knew what went wrong with the other plugs/coils but maybe I'll just never know...
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      05-22-2019, 10:22 PM   #12
drodrig2
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I wonder if these cars only like OEM coils/plugs and not brands of coils/plugs RockAuto sells?
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      05-23-2019, 09:53 AM   #13
stevemg9
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Quote:
Originally Posted by drodrig2 View Post
I wonder if these cars only like OEM coils/plugs and not brands of coils/plugs RockAuto sells?
Could be, but I feel like that shouldn't be the case. The plugs I got were the same Bosch plugs with the exact same part number as the OEM plugs (ZR5TPP33S). The only difference is that the OEM ones have "BMW" printed on them and the ones I bought had "Double Platinum" printed on them.

As for the the coil packs I couldn't say. Both the OEM and RockAuto coil packs were Delphi parts and they looked almost identical except the OEM coils had a white spot on top and RockAuto ones had a black spot.

Also I followed a YouTube video for the install process and that guy used the exact same plugs from RockAuto and didn't seem to have an issue.

https://www.youtube.com/watch?v=Dn0SInoL_c8
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      05-23-2019, 09:57 AM   #14
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Quote:
Originally Posted by stevemg9 View Post
Could be, but I feel like that shouldn't be the case. The plugs I got were the same Bosch plugs with the exact same part number as the OEM plugs (ZR5TPP33S). The only difference is that the OEM ones have "BMW" printed on them and the ones I bought had "Double Platinum" printed on them.

As for the the coil packs I couldn't say. Both the OEM and RockAuto coil packs were Delphi parts and they looked almost identical except the OEM coils had a white spot on top and RockAuto ones had a black spot.

Also I followed a YouTube video for the install process and that guy used the exact same plugs from RockAuto and didn't seem to have an issue.

https://www.youtube.com/watch?v=Dn0SInoL_c8
The Bosch coils on my old E92 335i was a known failure point. I would assume they would've corrected the issue since but who knows. I know once I replaced my Bosch with Delphi, I had no issues at all. Once the coils on this car goes, I'm going with Delphi again. BMW uses both brands as OEM parts.
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      05-23-2019, 11:17 AM   #15
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When it comes to electronics, spark plugs, and similar, I will use nothing but true factory OEM parts. I've never seen a brand so dependent on using OEM parts for ignition and fuel injection, but it's true and not worth the risk as similar issues have been reported by others.
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      05-23-2019, 12:05 PM   #16
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Quote:
Originally Posted by XutvJet View Post
When it comes to electronics, spark plugs, and similar, I will use nothing but true factory OEM parts. I've never seen a brand so dependent on using OEM parts for ignition and fuel injection, but it's true and not worth the risk as similar issues have been reported by others.
Funny thing is, BMW uses both Bosch and Delphi as OEM coils. With the E92/E90, I don't know if it was model year dependent, but once I changed out to Delphi, my car was good to go. I had 2 of the Bosch coils go out on me so if I experience coil failure in this car, I will skip a Bosch replacement and go straight to changing out all to Delpi for sure.
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      05-29-2019, 02:56 PM   #17
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Quote:
Originally Posted by stevemg9 View Post
Thanks for the input guys. I had the indy shop swap the original cat back in. Good news is they only charged me $50, bad news is they never hooked up the oxygen sensor - guess you get what you pay for. After the terrible 1.5 mile drive home in limp mode, I swapped back in the original spark plugs and coil packs - that's when I noticed the connector for the O2 sensor was just hanging loose. Started it up one last time and had some hard codes for misfires on 5 cylinders and and a oxygen sensor fault.

BMW told me that i needed new spark plugs and that "all of the ignition coils were exhausted." They also tested the O2 sensor and said it was faulty and needed to be replaced. I'm not sure if that code was thrown because I drove the car for a mile and a half without the sensor plugged in or because the sensor actually was faulty and I just hadn't driven it long enough to get that code before.

Either way, new plugs, coils, and an O2 sensor installed by BMW seemed to fix everything. The coils and O2 sensor were covered under CPO warranty so that was a relief. I wish I knew what went wrong with the other plugs/coils but maybe I'll just never know...
Glad that your warranty covered the plugs and coils. No telling what really happened there.
I have aftermarket plugs on mine they are NGK with factory coils but this was recommended by the BM3 tune / instructions so I gapped them and threw them in there myself with youtube assistance. So far car is running great. I may replace the coils soon with some better ones.
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      11-11-2020, 12:58 PM   #18
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Quote:
Originally Posted by MemphisPete901 View Post
Glad that your warranty covered the plugs and coils. No telling what really happened there.
I have aftermarket plugs on mine they are NGK with factory coils but this was recommended by the BM3 tune / instructions so I gapped them and threw them in there myself with youtube assistance. So far car is running great. I may replace the coils soon with some better ones.
Cvs
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      12-08-2020, 03:00 PM   #19
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misfirings after plug change 328ix

The intermittent misfirings are driving me nuts.
My car: 2011 BMW 328ix, 126,000 miles

Same problem: at 125,000 miles I replaced plugs, plus 2 coil packs for good luck.
I bought Napa spark plugs, with identical stamped numbers to BMW: LZFR6AP11GS. I did not measure or change the gapping, looked good and consistent out of the box.
Result: Immediate misfirings on #3,4, and 5.

I "fiddled" with coil connectors, wiggling and reconnecting, and pushed down hard to seat coil packs, gradually the firing smoothed out, I can't imagine why because I really changed nothing.
Plug #4 would occasionally misfire.
I kept clearing codes (Bavarian Tech Enthusiast reader), and "fiddling", finally it ran well, no codes.

Ran great for 6 weeks, with occasional momentary misfire, annoying but did not set a code.

Now, misfiring often again, stuttering on acceleration, missing also at idle, Cyl #4 per the code reader.
Other factors:
-happens to be a cold snap in December
-I confess to putting in 89 Octane this tank (I usually go for Premium or Super but have occasionally gone lower without problem)

So today I again connected the code reader, cleared code Cyl#4 misfire, drove the car hard, misfire returns.
Repeat, clear code, drive, car runs fine! No codes! I'm an engineer, I hate when problems just go away, they are sure to return.

If this unhappy intermittency repeats again later I suppose I'll have to change to BMW spark plugs. What else could explain the dealership success with plug replacement?

There happen to be two different codes, for example:
-29DO misfirings, cylinder 4 (is this detected by the acoustic knock detector, absence of sound?)
-2E1B ignition, cylinder 4 (is this a coil failure, or intentional with-holding of ignition, say due to detonation?)

I will say I noticed misfirings on hard acceleration, but occasionally idling too. My ears aren't good enough to pick up detonation, if that were happening. But this problem began with change of plugs 2 months ago.
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      12-13-2020, 11:22 AM   #20
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Oops, my bad.
Plug #4 was un-tightened.
Now tight, codes cleared, car runs great.
Case closed.
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