# 328d rough idle



## harveyinfl (Aug 14, 2013)

My 2014 328d - 30K miles has a rough idle when stopped. It does not happen all the time; but, seems to be more often lately. In fact the engine has stalled twice. I have added the product called "911 Diesel Additive" to remove any water from the fuel. No change after a full tank of use.

Dealer has no idea what the problem is. There are no dash red light to show a fault.

Any others have had a problem?


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## F32Fleet (Jul 14, 2010)

PowerService 911 was probably the worst product to add because your fuel will never gel in your climate. 

Try their grey bottle product. You DO NOT need the winter formula (white bottle). Maybe you have some injectors that are slightly dirty.


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## Roddd (Nov 15, 2014)

I'm a fan of Diesel Kleen. I run <2 ounces per tank. It really quiets the motor down and smooths it out in my 328d, as well as my Duramax. Has the dealer changed the fuel filter yet? That would be my first guess. It's covered under the 50,000 mile warranty.


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## harveyinfl (Aug 14, 2013)

Problem solved. The dealer called last week and informed me they had a 328d in the shop with the same problem and would let me know the results. The SM called today and told me they solved the problem.

The oxygen sensors before and after the cat were reading differently causing the rough idle while the car was stopped. The engine even stalled a few times over the past few weeks. He did not understand why the check engine light did not give a warning. Off to the shop next week.


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## robster10 (Oct 8, 2012)

A little dirty in there. Italian tune up time!:neener::neener::neener:


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## harveyinfl (Aug 14, 2013)

90 miles driven after the senors before and after the cat were replaced, I started to get rough idle again. A few week later the car was put back into the shop and spent a week there. After much delayed correspondence between the dealer and BMW, the dealer was told to remove the throttle body and look for soot build-up. The car has 31,000 miles and I changed the motor oil and filter every 5K miles. 

This is what they found. They also removed and cleaned the MAP sensor. This is unbelievable.


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## Roddd (Nov 15, 2014)

Harvey, 
What kind of driving do you do? I'm mostly highway, 65 miles to work and 65 right back. I have 54,000 on my 328d and haven't had any issues (knock on wood).


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## Master_Chase (Jun 8, 2015)

harveyinfl said:


> 90 miles driven after the senors before and after the cat were replaced, I started to get rough idle again. A few week later the car was put back into the shop and spent a week there. After much delayed correspondence between the dealer and BMW, the dealer was told to remove the throttle body and look for soot build-up. The car has 31,000 miles and I changed the motor oil and filter every 5K miles.
> 
> This is what they found. They also removed and cleaned the MAP sensor. This is unbelievable.


Welcome to the world of EPA crippled diesels.


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## KeithS (Dec 30, 2001)

harveyinfl said:


> ...After much delayed correspondence between the dealer and BMW, the dealer was told to remove the throttle body and look for soot build-up. The car has 31,000 miles and I changed the motor oil and filter every 5K miles.
> 
> This is what they found. They also removed and cleaned the MAP sensor. This is unbelievable.


Well that kinda of tells the story that while the newer BMW diesels may be better with the issue of building up carbon, it's FAR from eliminated.


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## whatnxt (Apr 10, 2011)

Bottom line is that you should not baby these. The stated Italian Tune-up or "drive it like you stole it" is not a bad approach every once in a while. Driving a diesel easily and for short trips is not good, long-term.


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## John Galt (Jul 21, 2012)

That sir, is carbon build-up caused by bio-diesel content greater than 5%. I had a 2014 X5 35d that had CBU at 46,xxx miles and I drove it extensively on the highway, aggressively, you name it. None of that mattered (I put on between 50,000 and 55,000 miles per year). What it all comes down to is bio-diesel content greater than 5%. This was DIRECTLY FROM BMW NA. They are supposedly working on a cleaning method that does not require tearing down the engine which they had to do on my 35d. The estimated cost of that "service" would have been between $5,000 and $6,000 per the dealer, however it was still covered under the factory warranty. Here's the REAL rub: BMW NA will not cover CBU removal on any extended warranty, factory or 3rd-party. 

-John


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## BB_cuda (Nov 8, 2011)

Harvey, Your throttle body looks way worse than my M57 equipped 335D throttle body did when I pulled it out the first time. I removed it at 27,000 miles and cleaned it and the EGR valve. I also do short trip driving and yes I know that isn't good. I'm likely in the minority when I say this. I don't think driving it like you stole it will help much. Unless you have a death wish, you will have to drive it normal some times lest you rear end somebody or drive recklessly. I feel more aggressive driving will only delay how quickly the gunk builds up. I used to say the exact same thing as all of you about standing on it to keep CBU away.

There is an answer but you have to be in a non emission check state. I will leave it at that. I pull my throttle body/EGR valve about once a year. It is always so clean except for a small amount of oil film on it and yes I'm running an oil catch can.

I run the gray bottle of Diesel Kleen though I'm considering changing over to Optilube as its supposed to be better from a wear scar rating perspective. Before someone attacks me on the "no additives" front, I departed from conventional practice a while back as about 100 lbs of equipment isn't rolling down the road with me anymore . I pulled my intake manifold recently and switched in a used/cleaned one.


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## harveyinfl (Aug 14, 2013)

The problem may be that I drive my Porsche like I stole it; but that's at Sebring. When I drive around town, I'm resting from all the track time.

I just received another pix of the temp sensor and inside the intake manifold. I just spoke with the service manager who said that BMW would not clean the intake until the engine does not operate properly. 

I guess I should have purchased a car with a gasoline engine.


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## John Galt (Jul 21, 2012)

harveyinfl said:


> I just spoke with the service manager who said that BMW would not clean the intake until the engine does not operate properly.


WRONG! Your vehicle IS NOT operating as designed and with less than 30,000 miles on it. Believe me, if you push them hard enough, they'll have a come-to-Jesus and find that they're suddenly ready to properly service your vehicle and perform the CBU removal of the entire engine, intake and all. I'd begin a case with BMW NA about this if you haven't already. Also if you have another BMW dealership in the area, go to them with your grievance. Is this your first BMW from that dealership?

-John


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## glangford (Dec 11, 2013)

I probably have this happening. I've noticed an occasional weird idle very intermittently. Sort of like the engine is surging, then dropping back down, but the tach doesn't move (sounds like a rhythmic surging). I mentioned it to the dealer, and he said there was nothing to do without a fault code.


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## Doug Huffman (Apr 25, 2015)

glangford said:


> I probably have this happening. I've noticed an occasional weird idle very intermittently. Sort of like the engine is surging, then dropping back down, but the tach doesn't move (sounds like a rhythmic surging). I mentioned it to the dealer, and he said there was nothing to do without a fault code.


Like the ECU maintaining idle speed constant even with varying AC and electrical loads?


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## glangford (Dec 11, 2013)

Doug Huffman said:


> Like the ECU maintaining idle speed constant even with varying AC and electrical loads?


No, not like that. It doesn't do it all the time.


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## F32Fleet (Jul 14, 2010)

harveyinfl said:


> 90 miles driven after the senors before and after the cat were replaced, I started to get rough idle again. A few week later the car was put back into the shop and spent a week there. After much delayed correspondence between the dealer and BMW, the dealer was told to remove the throttle body and look for soot build-up. The car has 31,000 miles and I changed the motor oil and filter every 5K miles.
> 
> This is what they found. They also removed and cleaned the MAP sensor. This is unbelievable.


Don't change the oil every 5k miles!!!!

Doing so keeps introducing lighter aromatics into the intake and you're preventing the boundary layer of protection from fully developing.

btw..Soot is really not that bad compared to the M57 engine.


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## glangford (Dec 11, 2013)

F32Fleet said:


> Don't change the oil every 5k miles!!!!
> 
> Doing so keeps introducing lighter aromatics into the intake and you're preventing the boundary layer of protection from fully developing.
> 
> btw..Soot is really not that bad compared to the M57 engine.


With synthetic there shouldn't be as big a spread in molecular weight of the oils in the mixture, so not much in terms of lighter aromatics to boil away. In fact a group IV or V oil should be totally free of them, basically being a single molecule throughout the oil.

Might make me want to try Redline LL-04 equivalent.

One of its attributes is:

"Less evaporation than other synthetics for improved efficiency and ring seal"


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## F32Fleet (Jul 14, 2010)

glangford said:


> With synthetic there shouldn't be as big a spread in molecular weight of the oils in the mixture, so not much in terms of lighter aromatics to boil away. In fact a group IV or V oil should be totally free of them, basically being a single molecule throughout the oil.
> 
> Might make me want to try Redline LL-04 equivalent.
> 
> ...


ACEA C3 allows max NOACK under 13. It's low but no where near say an all ester (Redline). This level has been standard with the spec for a long time AND allows synthetic oils to contain a mixture of Group 3 (carrier for additive),4, and 5.


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## 3ismagic# (Mar 17, 2011)

Wow at 31k miles you actually broke my record for CBU.


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## YozhDzl (Mar 5, 2014)

John Galt said:


> That sir, is carbon build-up caused by bio-diesel content greater than 5%. I had a 2014 X5 35d that had CBU at 46,xxx miles and I drove it extensively on the highway, aggressively, you name it. None of that mattered (I put on between 50,000 and 55,000 miles per year). What it all comes down to is bio-diesel content greater than 5%. This was DIRECTLY FROM BMW NA. They are supposedly working on a cleaning method that does not require tearing down the engine which they had to do on my 35d. The estimated cost of that "service" would have been between $5,000 and $6,000 per the dealer, however it was still covered under the factory warranty. Here's the REAL rub: BMW NA will not cover CBU removal on any extended warranty, factory or 3rd-party.
> 
> -John


Doubt it has anything to do with biodiesel. It's a simple oil vapour and soot mixed together. Welcome to the club boys. 335d crowd is very familiar with it and we were hoping 328d will be better, but looks like same issues. If I would be buying a new diesel first thing i would do is block the EGR. Love how BMW stories keep going, biodiesel, additives, drive harder, etc.


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## bimmerup-sonny (May 29, 2013)

BB_cuda said:


> Harvey, Your throttle body looks way worse than my M57 equipped 335D throttle body did when I pulled it out the first time. I removed it at 27,000 miles and cleaned it and the EGR valve. I also do short trip driving and yes I know that isn't good. I'm likely in the minority when I say this. I don't think driving it like you stole it will help much. Unless you have a death wish, you will have to drive it normal some times lest you rear end somebody or drive recklessly. I feel more aggressive driving will only delay how quickly the gunk builds up. I used to say the exact same thing as all of you about standing on it to keep CBU away.
> 
> There is an answer but you have to be in a non emission check state. I will leave it at that. I pull my throttle body/EGR valve about once a year. It is always so clean except for a small amount of oil film on it and yes I'm running an oil catch can.
> 
> I run the gray bottle of Diesel Kleen though I'm considering changing over to Optilube as its supposed to be better from a wear scar rating perspective. Before someone attacks me on the "no additives" front, I departed from conventional practice a while back as about 100 lbs of equipment isn't rolling down the road with me anymore . I pulled my intake manifold recently and switched in a used/cleaned one.


I agreed that "driving like you stole it" only delay CBU I drive my card hard every morning on a canyon road, then purposely drive on 4th gear on freeway for a 2-3 miles. My 335d had no issues from 27K - 71K miles. Then it started to throw MAF code, power loss was noticed. Did the CBU clean at an indy garage, power came back, car ran perfectly until 77K miles, now threw bunch of "injector issues". I've read that it may have to do with SW updates that needed after the CBU cleaning, will do that this afternoon.

I will post the results tomorrow


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## bimmerup-sonny (May 29, 2013)

bimmerup-sonny said:


> I agreed that "driving like you stole it" only delay CBU I drive my card hard every morning on a canyon road, then purposely drive on 4th gear on freeway for a 2-3 miles. My 335d had no issues from 27K - 71K miles. Then it started to throw MAF code, power loss was noticed. Did the CBU clean at an indy garage, power came back, car ran perfectly until 77K miles, now threw bunch of "injector issues". I've read that it may have to do with SW updates that needed after the CBU cleaning, will do that this afternoon.
> 
> I will post the results tomorrow


I don't want to hi-jack this thread, so I am posting my updates on my injector fault codes
on a separate thread with the correct title, if you want you can read it here:
http://www.bimmerfest.com/forums/sho...d.php?t=905004


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## Hoooper (Jun 17, 2013)

F32Fleet said:


> btw..Soot is really not that bad compared to the M57 engine.


I'm going to disagree. All he really has is an egr picture and inlet of the intake, the buildup in the m57 at these locations is really not that significant even when the engine barely runs. We would need to see a picture in the intake runners and at the valves to compare.


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## Gep9402 (Jan 13, 2017)

*Rough Idle At Startup only*

I have noticed a rough idle at startup only. It'll surge every few seconds, however if I drive it even 5 mins then It'll be fine. I never notice any rough idling on startup while in traffic or after the car has been running for a few minutes.

I have noticed it mostly if it has been sitting overnight. It's never stalled and I haven't noticed anything else unusual at startup. This isn't my first German diesel car so I'm used to the occasional rough idle, especially during DPF Regen, but have never noticed it on startup before.

My 328d is a 2014 with just over 21K on it. Just got it about a week and a half go. Any advice would be appreciated. If this is just normal on a cold startup then great, but I do have the CPO warranty on it so may just mention it to the dealer if it keeps up a few more weeks here. I just never noticed it on my previous diesel car at startup unless the temp was in the single digits or lower. The temp was over 40 here today and rainy.


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## Enthusiast 456 (Jun 23, 2014)

robster10 said:


> A little dirty in there. Italian tune up time!:neener::neener::neener:


Mine's started to do this too. Guess it's time for some seat time in Sport mode on the back roads.


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## imtjm (Oct 5, 2004)

Gep9402 said:


> I have noticed a rough idle at startup only. It'll surge every few seconds, however if I drive it even 5 mins then It'll be fine. I never notice any rough idling on startup while in traffic or after the car has been running for a few minutes.
> 
> I have noticed it mostly if it has been sitting overnight. It's never stalled and I haven't noticed anything else unusual at startup. This isn't my first German diesel car so I'm used to the occasional rough idle, especially during DPF Regen, but have never noticed it on startup before.
> 
> My 328d is a 2014 with just over 21K on it. Just got it about a week and a half go. Any advice would be appreciated. If this is just normal on a cold startup then great, but I do have the CPO warranty on it so may just mention it to the dealer if it keeps up a few more weeks here. I just never noticed it on my previous diesel car at startup unless the temp was in the single digits or lower. The temp was over 40 here today and rainy.


considering it's still covered under the new car warranty still, you should just bring it in.


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## JohnJan (Jan 28, 2017)

harveyinfl said:


> My 2014 328d - 30K miles has a rough idle when stopped. It does not happen all the time; but, seems to be more often lately. In fact the engine has stalled twice. I have added the product called "911 Diesel Additive" to remove any water from the fuel. No change after a full tank of use.
> 
> Dealer has no idea what the problem is. There are no dash red light to show a fault.
> 
> Any others have had a problem?


Try an engine flush with BG 109. This will get rid of the gunk & swarf accumulated in the engine sump. Recipe for Flush is :- 1 l’iter clean oil & rest pure BG 109 ( up to your max. Level of fluid fill for your engine say 5 litres?)
Run engine for 45 minutes. Drain completely and refill with clean fresh synthetic Oil.
This is the cheapest method to try first. See if it works. If not troubleshoot the Injectors.
I only use highest octane petrol I can get - we have 100 octane -Shell V power and add 2 bottles of Injector Cleaner to a full tank of petrol.
This sorted my injector problem out in situ without a messy job to remove injectors.
Keep Using the Injector Cleaner for 5/10 tank fills. A hell of a lot cheaper than replacing injectors at £300 a piece.


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## mattebury (Feb 2, 2014)

JohnJan said:


> Try an engine flush with BG 109. This will get rid of the gunk & swarf accumulated in the engine sump. Recipe for Flush is :- 1 l’iter clean oil & rest pure BG 109 ( up to your max. Level of fluid fill for your engine say 5 litres?)
> Run engine for 45 minutes. Drain completely and refill with clean fresh synthetic Oil.
> This is the cheapest method to try first. See if it works. If not troubleshoot the Injectors.
> I only use highest octane petrol I can get - we have 100 octane -Shell V power and add 2 bottles of Injector Cleaner to a full tank of petrol.
> ...



DO NOT PUT GASOLINE (PETROL) INJECTOR CLEANER INTO DIESEL!


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## JohnJan (Jan 28, 2017)

Course Not. 
I drive a petrol powered car & use a Petrol Injector Cleaner.
Those who drive a Diesel would use a Diesel Injector Cleaner.
Like Wynnes from Halfords. Clarro?


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## gryffishhawk (12 mo ago)

harveyinfl said:


> My 2014 328d - 30K miles has a rough idle when stopped. It does not happen all the time; but, seems to be more often lately. In fact the engine has stalled twice. I have added the product called "911 Diesel Additive" to remove any water from the fuel. No change after a full tank of use.
> 
> Dealer has no idea what the problem is. There are no dash red light to show a fault.
> 
> Any others have had a problem?


You've described my 2014 328d exactly! My 328d has around 53K now and the problem began around 20K. The problem happens at idle when in drive. If i shift into neutral or park it typically resolves the problem. Anyway, no one has any idea or suggestions. The dealer says without a code, assuming some default code, there's nothing to do, nothing to know. He said to video it and I did and the tech watched it. They did talk with BMW NA and decided to replace the mass air flow sensor or similar. Nothing changed or improved so apparently the answer is no one knows. Even BMW NA is clueless!! Not too comforting. Love the car otherwise but the rough idle is v disconcerting. Mentioned it to a friend with a diesel truck and he said well, that's a diesel. Implying its just part of the deal. Modern diesels have a ton of parts and complex emission and v high pressure fuel systems and if that were not enough American fuels now seem to be blended quite a lot with ethanol or biofuels and so, all I can determine is there are so many potential culprits it's damn near impossible to say anything with certainty or as some wise person suggested here...drive more, worry less...might be the best we can do. Sorry wish I could help!!!


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## Cconner (12 mo ago)

You need a Diesel Fuel Additive. I use Primrose 5007, it is the 1st DSL Fuel additive ever made. I also use Primrose 480M Engine Oil Additive w/ Liquid Moly-D.

The Diesel Fuel Additive (5007) is a must, I put 2oz in my Car every fill up and have had ZERO issues and I do all my own service.

Cetane is to Diesel what Octane is to Unleaded and the Diesel Fuel is this country is low on Cetane for a reason. They don’t make money selling you an engine, they make money selling you EGR Valves and DP Filters.
Please do not hesitate to reach out, I can send you a few quarts for Free, but I do sell it and it is the reason I bought a Diesel, well that and the MPG!

2018 Pearl White 328d Xdrive
Purchased at 19k miles now has 45k miles 
49 hwy mpg
44 city mpg


Chris Conner
THE CONNER GROUP
[email protected]


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## gryffishhawk (12 mo ago)

Cconner said:


> You need a Diesel Fuel Additive. I use Primrose 5007, it is the 1st DSL Fuel additive ever made. I also use Primrose 480M Engine Oil Additive w/ Liquid Moly-D.
> 
> The Diesel Fuel Additive (5007) is a must, I put 2oz in my Car every fill up and have had ZERO issues and I do all my own service.
> 
> ...


Thank YOU! It's great to learn more. You know I bought the car for the same reason insane MPG--sometimes 60+ when gently cruising--plus longevity always understood growing up that diesels were built.to.last! Plus there's something v appealing about compression ignition--all my gassers--spark ignition--engines seem to run so hot--and a cooler running engine in my hot climate seemed a good fit. The car is a blast to drive and as Hammond of Top Gear noted..."best car ever built"...he was probably referring to the European 320d version but those vehicles seem to share a lot of DNA with our 328d (both use the N47 2 liter engine, etc) so, fingers crossed

ADDITIVES AND FUEL
Anyway, I did use my first additive last month a can Liqui-Moly Super Diesel Additive (10.2oz can) out of Germany--read that Germans know diesel so a German additive was the way to go. Was going to continue to add a can every 1250mi or so. 

I also purchased some Opti-Lube Summer Lube+Cetane--in 8+ years the car has never seen below 37 degrees F and typically operates in 80-90 degree heat most of the year. I've not tried the Opti-Lube yet.

The car has only ever been fueled with BP Diesel. Of course, there's no info on the BP pump re: cetane ratings, bio-diesel content, etc. Have tried to contact BP of NA and got no where as to fuel quality or content. Car's manual said BMW recommends BP fuels plus BP says they guarantee their fuels against any fuel-related problem and so, this is how I made this decision. I Keep the tank topped off as much as practical to limit potential condensation in the tank.

Excited to learn more about the products you mentioned--thanks for taking the time and sharing--SO appreciated!!


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## alacey (Mar 14, 2018)

gryffishhawk said:


> You've described my 2014 328d exactly! My 328d has around 53K now and the problem began around 20K. The problem happens at idle when in drive. If i shift into neutral or park it typically resolves the problem. Anyway, no one has any idea or suggestions. The dealer says without a code, assuming some default code, there's nothing to do, nothing to know. He said to video it and I did and the tech watched it. They did talk with BMW NA and decided to replace the mass air flow sensor or similar. Nothing changed or improved so apparently the answer is no one knows. Even BMW NA is clueless!! Not too comforting. Love the car otherwise but the rough idle is v disconcerting. Mentioned it to a friend with a diesel truck and he said well, that's a diesel. Implying its just part of the deal. Modern diesels have a ton of parts and complex emission and v high pressure fuel systems and if that were not enough American fuels now seem to be blended quite a lot with ethanol or biofuels and so, all I can determine is there are so many potential culprits it's damn near impossible to say anything with certainty or as some wise person suggested here...drive more, worry less...might be the best we can do. Sorry wish I could help!!!



I have owned many diesels trucks and the rough idle your are talking about is not just a diesel thing. My 2014 328d had the same issue. Thought it was an injector at first, but it still did it after I fixed that issue. Started adding some diesel additives and the rough idle went away. Some did better than others at keeping the rough idle away. Hotshot's Secret did the best and I did notice the best fuel mileage increase versus the others. Every time I stopped using it the rough idle would get progressively worse until I used it again.


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## gryffishhawk (12 mo ago)

Thanks


alacey said:


> I have owned many diesels trucks and the rough idle your are talking about is not just a diesel thing. My 2014 328d had the same issue. Thought it was an injector at first, but it still did it after I fixed that issue. Started adding some diesel additives and the rough idle went away. Some did better than others at keeping the rough idle away. Hotshot's Secret did the best and I did notice the best fuel mileage increase versus the others. Every time I stopped using it the rough idle would get progressively worse until I used it again.


Thanks! You know the fuel filler cap has this* No Additives* like right in your face and all and so, was hesitant to try plus there's so many additives out there and all--kinda confusing. Appreciate learning what worked best for you. Sounds like we've got the same car. What's a mystery is why it typically only idles roughly when fully up to temp and why shifting from drive to neutral fixes the problem. Maybe it's a regen and/or DEF fluid thing happening at those times? Dunno but do recall something in the BMW manual about rough running during DEF operations?

Who knows. This is my first diesel and I love it and can't get 'em anymore so just hoping/trying to make it last, not damage what appears to be an amazing feat of german engineering!!


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## alacey (Mar 14, 2018)

gryffishhawk said:


> Thanks
> Thanks! You know the fuel filler cap has this* No Additives* like right in your face and all and so, was hesitant to try plus there's so many additives out there and all--kinda confusing. Appreciate learning what worked best for you. Sounds like we've got the same car. What's a mystery is why it typically only idles roughly when fully up to temp and why shifting from drive to neutral fixes the problem. Maybe it's a regen and/or DEF fluid thing happening at those times? Dunno but do recall something in the BMW manual about rough running during DEF operations?
> 
> Who knows. This is my first diesel and I love it and can't get 'em anymore so just hoping/trying to make it last, not damage what appears to be an amazing feat of german engineering!!



Neutral is not placing a load on the engine. Park is placing a slight load on the engine and your foot on the brake is holding the car back. Not all injectors inject the same amount of fuel at all times. The computer(or DDE) try and adjust each ejector so they inject the same amount buy they will always be a fraction of a percentage off. This is even harder when you have one or more injectors that are dirty or clogged with carbon causing erratic spray patterns which in turn causes rough idle especially under light load. The DDE will have to adjust the injection of the other injectors to compensate for the dirty injector(s). 

I know this has nothing to do with the EGR or SCR/DEF system because mine...... fell off years ago if you know what I mean and my car still had a rough idle. I will also say that the reason why many manufacturers diesel stopped recommending additives was mainly due to the effect they had on emissions systems especially the SCR. Depending on which additive you use and how much, it could increase your ash content along with other ill effects toy your sensors. So regardless of whether or not it is better for your engine, it may not be better for emissions systems and you need to pass emissions above all else or you can't sell your vehicle in the US.


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## gryffishhawk (12 mo ago)

alacey said:


> Neutral is not placing a load on the engine. Park is placing a slight load on the engine and your foot on the brake is holding the car back. Not all injectors inject the same amount of fuel at all times. The computer(or DDE) try and adjust each ejector so they inject the same amount buy they will always be a fraction of a percentage off. This is even harder when you have one or more injectors that are dirty or clogged with carbon causing erratic spray patterns which in turn causes rough idle especially under light load. The DDE will have to adjust the injection of the other injectors to compensate for the dirty injector(s).
> 
> I know this has nothing to do with the EGR or SCR/DEF system because mine...... fell off years ago if you know what I mean and my car still had a rough idle. I will also say that the reason why many manufacturers diesel stopped recommending additives was mainly due to the effect they had on emissions systems especially the SCR. Depending on which additive you use and how much, it could increase your ash content along with other ill effects toy your sensors. So regardless of whether or not it is better for your engine, it may not be better for emissions systems and you need to pass emissions above all else or you can't sell your vehicle in the US.


Great to learn! Yup, my car is still all original OEM, emissions, etc...no plans to delete anything. i'm in tampa FL and i don't think the car has to pass any kind of emissions test--no one seems to care a lick about any of that down here.

anyway, sounds like you suspect the injectors? like one or more injectors might be fouled, plugged, etc? can these be cleaned or replaced? wouldn't the car's computer throw a code or something, CEL, etc if the injector had an issue?

thx for helping out!


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## alacey (Mar 14, 2018)

gryffishhawk said:


> Great to learn! Yup, my car is still all original OEM, emissions, etc...no plans to delete anything. i'm in tampa FL and i don't think the car has to pass any kind of emissions test--no one seems to care a lick about any of that down here.
> 
> anyway, sounds like you suspect the injectors? like one or more injectors might be fouled, plugged, etc? can these be cleaned or replaced? wouldn't the car's computer throw a code or something, CEL, etc if the injector had an issue?
> 
> thx for helping out!


They can be cleaned either by taking them out and cleaning them or by fuel additives. Some additives do a better job than others and many are just more concentrated forms of the fuel additives that fuel suppliers(Shell, BP, etc...) already add to their fuel. You can definitely replace the injectors at around $350 a pop plus labor. If you do them yourself then you will need special tools like calibration software so you can program the trim code off of each injector. This trim code tells the DDE how much fuel to add to the injector to keep it balanced.

A dirty injector will not always throw a code. It depends on how bad it is. Each injector has an allowable min/max range that it can adjust to without throwing a code. It is when they get past these limits that they will throw a code.

Here is a video kind of explaining how you can check for injector imbalance(with proper tools). It is for a Duramax diesel, but same thing applies to our BMW's.






Here is another video showing a balance test being performed on a diesel Powerstroke diesel truck so you can get a rough idea of how they are all over the place especially at idle. Notice how it is mainly at idle and light load that they are sporadic and it smooths out under higher load.


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## alacey (Mar 14, 2018)

Double post


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