# 2009 BMW 128i Rough Idle & Misfires



## grandpuba (Mar 5, 2020)

Hey guys! 
I drive a 2009 BMW 128i with 81,000 km and have been having rough idle for quite some time, along with some misfires. Here's a little history. Had my car go into limp mode one day, so immediately took it in to get looked at. Got the codes read, and was told I was misfiring on different cylinders, and when cleared, it would come back, but the misfires would jump around cylinders. When further investigated, was told 5/6 cylinders had oil in them, due to a leaking valve cover gasket. Replaced the valve cover gasket, replaced all spark plugs, replaced all ignition coils, replaced cabin filter, and air filter. When I took to back, I noticed the car still ran a little "off" when idle, but thought maybe it needed time to adjust to new parts, so drove it more. One time when trying to merge into highway, and putting the pedal down enough to accelerate, the car went, but kind of shook with some hesitation, and the check engine light came on. I pulled over, and the car was shaking, so i shut the car off, restarted, and everything was normal again. Took it in again to get the code read, and told I misfired on cylinders 5 & 6 and was told this shouldn't be happening with all the work I had done. They cleared code and told me to drive it some more, and if it happened again, they'd have to rip everything apart again to make sure everything was seated correctly. Took it back, drove for about a week and a half, and again, under same conditions of trying to accelerate onto highway, check engine light came back on and I pulled over, restarted, and everything cleared again. I have it booked in Monday to get looked at, but was thinking I could ask if anyone's dealt with similar issues, so I might be able to give the shop an idea of what to check next, if everything checks out with what I've already replaced. Here a couple notes :
Idles at 6500 rpm, but seems to want to be at 7000, and will sometimes on rare occasion run idle at 7000 and be smooth. 90% of times runs at 6500, but can feel a rumble, almost similar to a gallop. 
When engine is cold, going into 2nd you can feel the car almost buck, but accelerating through the remaining gears is clean and smooth. Once the car really warms up, the bucking is minimal, and it seems to shifts almost seamlessly, with only a slight bit of that feeling. 
Just ran Techron through for a full tank, and noticed little to no change.


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## jaye944 (Jul 5, 2015)

could be a number of things, but they would all give codes, get an actual print out of the codes and post here

somethings which could cause problems (in no order)

1> Vanos Solenoid
2> Eccentric shaft sensor
3> Camshaft sensors (2)
4>I only run with OEM plugs ' were the replacements gapped correctly (no need if OEM)
5> Bad earth on injector wiring
6> check battery cables and earthing as well 
7> possible vacuum leak 

was this a dealer or an indy

you need to see the full list of codes


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## grandpuba (Mar 5, 2020)

So here's a list of the fault codes I got last time :

29CC Absent Digital Motor Electronics (DME) combustion misfires, several cylinders

29D1 Absent Digital Motor Electronics (DME): cylinder 5 combustion misfires

29D2 Absent Digital Motor Electronics (DME): cylinder 6 combustion misfires

Work was completed at a trusted indy shop (as I don't even wanna know what BMW dealer would have charged for the work), and the spark plugs are listed as "DIO 3421 IRIDIUM SPARK PLUGS" so hopefully that provides more info...


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## grandpuba (Mar 5, 2020)

So here's a list of the fault codes I got last time :

29CC Absent Digital Motor Electronics (DME) combustion misfires, several cylinders

29D1 Absent Digital Motor Electronics (DME): cylinder 5 combustion misfires

29D2 Absent Digital Motor Electronics (DME): cylinder 6 combustion misfires

Work was completed at a trusted indy shop (as I don't even wanna know what BMW dealer would have charged for the work), and the spark plugs are listed as "DIO 3421 IRIDIUM SPARK PLUGS" so hopefully that provides more info...


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## jaye944 (Jul 5, 2015)

hey man, txs for that, so a couple of points

1> I have heard that non-OEM plugs can cause problems such as misfire. I have done a lot of research and if you google you will fine the same. I have only used OEM's no issues.

2> see if the fault follows, so if a single plug, swap plug 5 and 1 see if the code follows the plug, then swap the coil to see if the fault follows the coil pack, if the fault doesnt move,
your looking at a wiring problem to the coil pack or an earthing problem

this is where you really need a code reader  Aftermarket coils I think are fine, but if it were me I would put in OEM plugs,

When you pulled the cover, did you put everything back correctly ? could even be an injector issue, you may need to swap injectors

I would put OEM plugs in first

there's a well respected bimmer guy who gave the following advise*
"AND when you replace the spark plugs... only buy the plugs from a BMW dealer. The aftermarket plugs (even though they are the same part number and made by Bosch) are different somehow and cause misfiring codes to throw as well. USE only plugs bought from a dealer!! See my Park plug DIY for more of that."*

I


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## jaye944 (Jul 5, 2015)

you don't give your location, I'm in Canada, would love to help you I have the BMW software on my laptop,
cheers


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## grandpuba (Mar 5, 2020)

Hey man, thanks for all the valuable info. 
I think you're reiterating info I had already read, and thought myself, but wanted some more experienced knowledge, and figured this was a good place to start. So I appreciate you sharing...
I read about non- OEM plugs causing misfires (unfortunately after the replacements I mentioned being put in) in a handful of places, so thought maybe that could be the base of my issue. I was thinking of mentioning it to the shop when they call back today to let me know their findings, and see what they say (if they tell me everything checks out).
The issue with swapping the plugs and the coils to try and find the issue, is the problem is hard to "remake" ie : putting enough load on the engine that it shoots me the check engine light, and along with it, the codes. It doesn't happen with simple daily driving, but I would still like to get the issue resolved, as I know it's there.
I didn't do the work myself, and had a shop in town here do the work, so I can't really attest to them putting everything back together correctly. They've always been reliable in the past, so I like to trust they did. 
I have come to think if all those items checked out, that it could be an injector(s), which I'm hoping it's not, cause I know that can be pretty pricey. I've read you have to replace "a bank" at least at a time? (Not sure if this is true for the N52 engine, but have read it for the N54), and that you can't just replace the faulty one. In some cases people recommending to do all 6. It looks like the injector setup is different on the two engines, so not sure if that applies to mine or not. Maybe you have an idea? Either way, with that said, really hoping it doesn't come to that...
I'm from grand ol' Saskatchewan. Coldest place on Earth haha


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## jaye944 (Jul 5, 2015)

hey,

ok, so and this is the problem, is diagnosing the issue, the misfire, may read as a code but not on a CEL "sometimes" I found on mine, if you drop the gas pedal, that is enough to get a CEL, BUT in my case I was swapping parts, then putting my laptop on to pull a code and see if it made a change.

Sometimes I've heard that coils can be faulty just on the cusp and not throw codes as well

Even when I had it in with BMW, thats how they diagnosed it.

The problem is you have to methodically work through the problem, otherwise it can get hairy. If you don't have the BMW software there are some apps which can pull the BMW codes also depends if your gonna be wrenching yourself or not.

*Step 1: I would just swap the plugs out for OEM, that may indeed be your problem, WATCH out for hitting the gaps especially when re-fitting them, unless your guy's are doing this.*

Injectors you can replace one at a time, I've heard they actually need to be "coded" FFS :dunno: N52 & N54 are different, injectors and probably method are different, I would research N52 only for your car, I don't even look at N54.

I don't know which N52 you have, if the beauty cover is black you have the newer one mine is a 12, which is the newer one.

You can't really play swap the parts unless you can pull codes.

IF you are going to pull the plugs yourself, that would be easier.

OH SK, LOL, yeah that's a bit of a drive man. Pity dat GTA here !



grandpuba said:


> Hey man, thanks for all the valuable info.
> I think you're reiterating info I had already read, and thought myself, but wanted some more experienced knowledge, and figured this was a good place to start. So I appreciate you sharing...
> I read about non- OEM plugs causing misfires (unfortunately after the replacements I mentioned being put in) in a handful of places, so thought maybe that could be the base of my issue. I was thinking of mentioning it to the shop when they call back today to let me know their findings, and see what they say (if they tell me everything checks out).
> The issue with swapping the plugs and the coils to try and find the issue, is the problem is hard to "remake" ie : putting enough load on the engine that it shoots me the check engine light, and along with it, the codes. It doesn't happen with simple daily driving, but I would still like to get the issue resolved, as I know it's there.
> ...


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## grandpuba (Mar 5, 2020)

Sorry, I didn't follow the how the diagnosed it part...putting the pedal down and getting the codes you mean?
Well I have it in the shop currently, so hopefully I hear something back from them today, at least what codes they found with it. I think it's important to see (if it is in fact more misfires) if it stayed within those two cylinders again, or moved around to others. I'm dreading hearing the "everything's tight and looks good", cause if that's what I get, I'll mention the plugs possibly being an issue and see what they say. 
Injectors I'm not very familiar with, and this is my first beemer that I've ever had to consider that an issue, so I'm not as knowledgeable in that dept. That's why I wasn't sure about if you can just get away with replacing the defective one(s) or all have to be done at the same time. Most places I've read sound like it's bad to try and get away with just doing them one by one (cost aside). I have heard about the coding of them, so not sure if that's a task I want to try and tackle myself if that's the road I go down myself lol The N52 and N54 are very different, but I only brought that up because I wasn't sure if that had to do with replacing a "bank" of them at a time. Injectors with mine look like they just run all along a single rail, so thought maybe that would be proof I could get away with just doing 1 by 1. Do you know if there's been any known issues with the factory injectors? (presuming mine are factory). Just shocked something like that could possibly "go" at only 80,000 kms...
As far as I'm aware, that cover is black on my beast. 

Well what are you waiting for? Get to driving mannnnn. Road trip! haha I'll buy you some beers for your efforts! XD haha


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## jaye944 (Jul 5, 2015)

so what I meant, (at least on mine when my coil packs went)
when I put it under strain, i.e. pedal to the metal, it threw a CEL light right away, that's how I tested swapping the parts, gentle driving even acceleration didnt do it.
when I tested swapping parts out, I drove it round the block, and then put a laptop on it.
pretty much right away it threw codes but no CEL light.

If it's a good shop they should know how to diagnose stuff, I'm assuming they are swapping parts to prove whats wrong, a misfire in a cylinder, is one of 3 things, plug, coil, cable
if it's MULTIPLE cylinders, it more a cable issue, or ground. They generally go one at a time.

BUT.... it was recommended if a coil pack went OR the plugs started to get worn, to replace ALL the plugs, as the plugs cause a strain on the packs and they fail. Think they should be done every 50k, on my 2nd faulty coil pack I replaced all the plugs. I still had a 3rd coil go.

The N54 injectors had a known problem, the N52's generally a good, and you don't hear people with faulty injectors as a rule. Most N52 injectors are changed singly, but the 54 I hear on a bank. 52's are then coded, depending on who you ask.

On 80k you should do a spark plug set.

IF they say they did nothing and it's not throwing codes, I would insist they change the plugs for OEM's, all of them. and for good measure swap out the 5 & 6 packs as well for new ones.

I'm an OEM fiend, and generally get OEM

beers :thumbup: unfortunately I've not got and leave for a while. Rain check you eh,
if you plan on seeing Niagara Falls, I'm on the way, stop on by !



grandpuba said:


> Sorry, I didn't follow the how the diagnosed it part...putting the pedal down and getting the codes you mean?
> Well I have it in the shop currently, so hopefully I hear something back from them today, at least what codes they found with it. I think it's important to see (if it is in fact more misfires) if it stayed within those two cylinders again, or moved around to others. I'm dreading hearing the "everything's tight and looks good", cause if that's what I get, I'll mention the plugs possibly being an issue and see what they say.
> Injectors I'm not very familiar with, and this is my first beemer that I've ever had to consider that an issue, so I'm not as knowledgeable in that dept. That's why I wasn't sure about if you can just get away with replacing the defective one(s) or all have to be done at the same time. Most places I've read sound like it's bad to try and get away with just doing them one by one (cost aside). I have heard about the coding of them, so not sure if that's a task I want to try and tackle myself if that's the road I go down myself lol The N52 and N54 are very different, but I only brought that up because I wasn't sure if that had to do with replacing a "bank" of them at a time. Injectors with mine look like they just run all along a single rail, so thought maybe that would be proof I could get away with just doing 1 by 1. Do you know if there's been any known issues with the factory injectors? (presuming mine are factory). Just shocked something like that could possibly "go" at only 80,000 kms...
> As far as I'm aware, that cover is black on my beast.
> ...


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## grandpuba (Mar 5, 2020)

So I spoke to the guys at the shop, and again, they said she's misfiring on cylinders 5 & 6. Said they were running some diagnostics and numbers (didn't go into detail exactly how or what), and have a feeling that the injectors for those two are either starting to go, or have. I was dreading that, as I figured if the misfire didn't move, it was solely a problem local to those two cylinders (likely injector related). but if it moved, it could possibly be something else simple, like the plugs you mentioned. Said they'll take a better look tomorrow and get the cowling and all that pulled off (what a nightmare on these dang cars), and get a better idea, but at this point, he's convinced it's the injectors. Since you say there wasn't much noted problems with them, I'm a little surprised, and especially with the low mileage, to already be having so many issues with the car. I brought up whether all 6 need to be replaced, or if it's something I can just stay with changing the 2, and he made it sound like if it's only the 2 throwing misfires, to just change those. My only thought is that if those two are affected right now, aren't the other 4 not going to be too far behind? I glanced quick at prices on BMW, and they seem to be around $300 a piece, UGH! So I don't seem very fond of dropping $2000 on injectors when I just spent $1700.00 on all the other things mentioned previously.


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## BabyUnicornTaco (Jan 8, 2018)

I skimmed this thread but can you pull the ignition coils from 5 & 6 yourself and look down the spark plug tubes? 


Sent from my iPhone using Bimmerfest


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## grandpuba (Mar 5, 2020)

I'd have to be there in their shop to do it, and I don't think they're they're going to be too fond of the that idea unfortunately. I would doubt at this point it would be the coils, since they're literally maybe a month old, and the issue continued when i first got the car back, and improves slightly when driving. The chances of getting two lemon coils I think would be slim to none, no? Is that what you're possibly thinking? I think they'll likely look at that tomorrow, before placing blame on the injectors, but injectors was their hunch just from diagnostics they were running...


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## jaye944 (Jul 5, 2015)

hey, no what babytaco, is asking for you to check, is if there is any fouling in the cylinders, a wet plug or wet tube, indicates a problem with an injector, i.e. it's leaking.
also oil on the plugs would indicate another problem.

Yes I agree with you possibility of 2 coils "new" faulty, are non-existant. 

"If" they diagnosed correctly, and the fault has NOT moved, you have 2 possibilities (maybe 3)

* Plugs are misfiring, all 6 were changed for non-OEM type (to me all 6 are suspect)
* Commonality in the wiring or earthing for either the injectors or coil wiring (for 5&6) you can't swap cabling only the coils
* Injectors... but both ? (leaky or seals are a problem)

Misfires issue started after the valve cover was replaced, a lot has to happen and be disconnected and refitted.
I also assume no misfires before the ?

Issue is your not doing the work, and having to depend on a 3rd party,


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## grandpuba (Mar 5, 2020)

Oh I see. Again, I haven't much done work with BMW's, so I'm kind of new on the scene and trying to learn the tricks of the trade. They're supposed to get a little more into it today to find out what's going on, so I should have more to report in a little bit here, but I was aware that checking the plugs for moisture or oil can be a tell tale sign of a leaking injector or other issue. Also seen the screwdriver to the ear trick to listen, but not sure if this is applicable to ACTUALLY diagnose a stuck or plugged up injector properly. 

I'm confident these guys diagnosed the same misfire correctly, as they're pretty methodical and very thorough, and don't like having people throw money at things that don't need fixing. I can't tell you how much money they've saved me when it comes to fixing cars, and not because they're cutting corners. But yes, they told me it threw the exact same codes as it did the first time, that I reported I believe in my second response above.

My only issue with thinking the plugs are the issue, is that I would think the misfire would move around, or at least not stay consistently in the same two cylinders. But that could very well be up for debate until they rule out injectors not being the issue, as then at that point it would lead me back to thinking those are a possibility. 
When you say "injectors...but both?" you make it sound like it's hard to believe that two would go at the same time like that. If they're leaky or it's seals, is that a guarantee replacement I presume? Again, not familiar with anything injector related, so forgive my idiocy lol

No, I was actually experiencing the misfires before the valve cover was replaced, because I was getting oil in 5 of 6 cylinders - which led to me having to replace the coils and plugs in the first place. But even after that work was completed, I could tell there was a little hiccup during idle (probably not noticeable to your every day driver, but noticeable to me who drives the car daily).


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## jaye944 (Jul 5, 2015)

generally, you wouldn't get 2 injectors, or 2 coils or 2 plugs go, and yes your right about things moving around.

It's something that is common or just a fluke, it has to be diagnosed methodically, and if you trust your guy's then yes they should be able to find it

The "only" thing is non OEM plugs that I can see

let us know what they come up with, but discussion is pretty much moot, as somone else is doing the work, your just a middle man , I think at this point, you have all the information in your hands, let us know what they find, or dont



grandpuba said:


> Oh I see. Again, I haven't much done work with BMW's, so I'm kind of new on the scene and trying to learn the tricks of the trade. They're supposed to get a little more into it today to find out what's going on, so I should have more to report in a little bit here, but I was aware that checking the plugs for moisture or oil can be a tell tale sign of a leaking injector or other issue. Also seen the screwdriver to the ear trick to listen, but not sure if this is applicable to ACTUALLY diagnose a stuck or plugged up injector properly.
> 
> I'm confident these guys diagnosed the same misfire correctly, as they're pretty methodical and very thorough, and don't like having people throw money at things that don't need fixing. I can't tell you how much money they've saved me when it comes to fixing cars, and not because they're cutting corners. But yes, they told me it threw the exact same codes as it did the first time, that I reported I believe in my second response above.
> 
> ...


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