Rough start and poor mpg- are new plugs enough

Atx328 · 03-05-2017, 08:44 AM

My 2011 328i almost sounds like a diesel with a cold start in the morning. I am only getting about 20-21 mpg even with a good amount of highway driving thrown in. I should mention much of that is at 80-85 mph.

There are no codes being thrown, the rough start doesn't show up anytime later in the day and the engine runs super smooth. It does seem a bit sluggish having come from a Infiniti g35 previously but that was a larger and more powerful engine. Popping the auto over to sport mode provides a crisper response but then the mpg really goes south.

It's low mileage at 46k but I thought that I would try replacing the plugs first. Being an engineer I tend to try to only make one change at a time so I thought I would start with the plugs first to see what impact that has.

Is that a logical next step or am I being silly by not replacing the coils at the same time?

Anything else I should be considering?

AM330i · 03-05-2017, 09:21 AM

it's a very good possibility that your plugs are worn. I was having the same issue with my '11 328 around the same mileage. spark plug replacement interval is 60k so your pretty close anyway.

Flyboy161 · 03-05-2017, 09:23 AM

Plugs, coils, air filter, oil change (if you're not sure of the last time it was done). Did you buy this car used? At a dealer or from a private individual? By "no codes are being thrown", do you mean you've read the codes with an OBD2 reader or have you used INPA or Carly to check the them? The former just reads generic codes the are often inaccurate in my experience. The latter will read error codes stored deep in the various modules and show specific problems. Rough cold start can be a caused by a number of things, one of which is gummed up VANOS solenoids that aren't advancing your cams properly.

Some of these errors can show themselves in the modules without tripping the Service Engine Soon light.

Atx328 · 03-05-2017, 12:58 PM

Thanks for the clarification flyboy!

I purchased the vehicle from a private party but they had all service done at BMW so it was relatively easy to pull a detailed history. I have already purchased the plugs and air filter and the oil change was recent. I would like to avoid doing the coils early if they don't actually have an impact.

My previous daily driver was a mazdaspeed miata and I didn't have an issue tossing new parts at a problem when spark plus were $8 a set and coils were $40. With the obviously higher costs of BMW operations, I would like to avoid replacing parts that are working well.

I was referring to codes present when the check engine light is lit. I have access to a really great local Indy so I will ask him to pull any subsystem type codes the next time I visit his shop (probably this week).

I am interested in picking up a Carly as I strongly believe more data leads to better decisions. As a relative newby, will the tool work with my wife's N20 motor in her f30 as well?

Flyboy161 · 03-05-2017, 01:34 PM

Check their website. It looks like they do support F3x in the 3 series and 4 series. Seeing as you are an engineer, there is a lot of great information out there on the web in PDF format about these cars. In particular how the different modules communicate with each other via the various busses. A google search for "E90 complete vehicle pdf" should point towards the top manual. Then, once you open that file look at the bookmarks on the left of your screen. Search for each in turn, download and read each manual. Pick up a Bentley manual for 3 series. There is a PDF version of it as well, but it only goes up through 2010.

Here are two attachments to get you started

dannyhavok · 03-05-2017, 01:39 PM

I had these exact symptoms recently when my eccentric shaft sensor was failing. I was getting about 15L/100KM when I normally get 10-12 in mixed driving. It would also occasionally stall on startup.

AWSB328iM · 03-05-2017, 02:39 PM

Change the plugs first. I just had issues with misfires on my car at 60k miles and the issue has gone away. Plugs were $56 shipped on eBay. Watch a YouTube video about changing the plugs and it should take you around a hour.
Cold start idle has smoothed somewhat and mileage has increased around 1-1.5 mpg around town.

Plug replacement:

Plugs: https://www.ebay.com/itm/112316731791

Flyboy161 · 03-05-2017, 04:07 PM

I went ahead and uploaded almost all the documents I have from BMW University in a thread over in manuals.

http://www.e90post.com/forums/showth...6#post21370206

blackturbo · 03-05-2017, 04:09 PM

Your on the right track. I would suggest plugs first.

My mileage was changed when my Camshaft sensor(exhaust) was malfunctioning. I threw a check engine. Pulled the code, and replaced it. Mileage was back to normal.
When I have time next week I'll be replacing the other Camshaft sensor (intake). If that intake sensor fails, you can't even start your car. Your probably looking at 80,000 miles to replace the sensors and they are relatively cheap. Just get the vdo ones, bmw oem just puts a stamp on them and unchanged.

Good luck. Let us know if there's any change with the plugs.

Atx328 · 03-05-2017, 09:27 PM

Quote:

Originally Posted by dannyhavok

I had these exact symptoms recently when my eccentric shaft sensor was failing. I was getting about 15L/100KM when I normally get 10-12 in mixed driving. It would also occasionally stall on startup.

How did you end up diagnosing the eccentric shaft sensor?

Atx328 · 03-05-2017, 09:35 PM

Quote:

Originally Posted by Flyboy161

I went ahead and uploaded almost all the documents I have from BMW University in a thread over in manuals.

http://www.e90post.com/forums/showth...6#post21370206

Wow that is just awesome!

I have to confess that I am a software engineer and I don't have much of a knack for mechanical problems. But while I tend to take longer than other folks to perform dyi projects, I get more of a sense of accomplishment when I do. I guess since it's more of a challenge, I give myself more credit for the higher degree of difficulty.

absentmathis · 03-05-2017, 10:53 PM

Plugs are not going to change much of anything.

Flyboy161 · 03-05-2017, 11:14 PM

Quote:

Originally Posted by Atx328

Wow that is just awesome!

I have to confess that I am a software engineer and I don't have much of a knack for mechanical problems. But while I tend to take longer than other folks to perform dyi projects, I get more of a sense of accomplishment when I do. I guess since it's more of a challenge, I give myself more credit for the higher degree of difficulty.

Read. Pay attention to how things work. Ask questions. Take your time. There is no such thing as too slow when you do it yourself. We have a motto in my business; No faster than safe. It carries over into all aspects of life. There are lots of folks in these forums who can help you along the way, and some that will scoff at you. Never take it personally, it is after all their weakness of character that drives them. I'm an old school mechanic, who's been dealing with 1950's technology for almost 30 years. Now, I am thrust into the world of data busses and smoke and mirror boxes on modern aircraft. I will confess, I don't know it all, when it comes to these cars. Never will, but journey is half the fun.

TemjinX2 · 03-06-2017, 12:36 AM

The engine in the e9x series engines are pretty simple compared to todays car's, so i wouldn't worry. I agree, with everyone else, just take your time, read through some of the diy's and its pretty straight forward.

ctuna · 03-06-2017, 02:34 AM

If it only happens on the first start of the day it could be a weak
battery.
Try putting a full charge on the battery to see if things change for the
first start problem.

http://www.e90post.com/forums/showthread.php?t=13504

electical e90 pdf
http://www.google.com/url?sa=t&rct=j...,d.cGU&cad=rja
http://www.google.com/url?sa=t&rct=j...85464276,d.cGU
http://www.google.com/url?sa=t&rct=j...85464276,d.cGU

these cars don't get that good a mileage in town freeway is pretty good.

You could try reseting the adaptions .

Atx328 · 03-18-2017, 01:08 PM

So I just got back from Vacation a few days ago so I wasn't able to find time to swap out my plugs until this morning.

Plugs 3-6 looked pretty good but they definitely had a wider gap than the new ones. Plug 2 was almost at the recommend gap and then 1 was inbetween 2 and 3-6. If I was going to be cheap, it looks like I could have simply cleaned them up, regapped them to factory specs and run another 15K easily.

However, I wasn't that foolish and when i put the new plugs in, it seems like the initial start was much smoother. I will have to keep an eye on my results the next several days and also reset the mpg monitor.

One thing that I found surprising was the lack of anti-seize on the factory plugs. That took the most torque to break each one loose that I have ever experienced for a plug on any of the 20+ vehicles that I have owned. Either that or the torque wrench operated by Otto was set to "manly" when they were initially installed.

Flyboy161 · 03-19-2017, 10:56 AM

Great followup! Keep us posted.

roundle · 03-19-2017, 11:41 AM

The N52 likes plugs every 50K miles or so. Your coils are probably fine for another 50K miles.

Might be worth pulling the VANOS solenoids out and, depending upon how they look, giving them a quick bath in brake cleaner.

Might be interesting to post a good quality video with sound to help people understand the problem you are trying to solve. Are you getting a knocking sound? If yes, could be lifter related (but unlikely given that you have a 'new' N52 head).

NiNeTyOne · 03-19-2017, 01:57 PM

Quote:

Originally Posted by Atx328

So I just got back from Vacation a few days ago so I wasn't able to find time to swap out my plugs until this morning.

Plugs 3-6 looked pretty good but they definitely had a wider gap than the new ones. Plug 2 was almost at the recommend gap and then 1 was inbetween 2 and 3-6. If I was going to be cheap, it looks like I could have simply cleaned them up, regapped them to factory specs and run another 15K easily.

However, I wasn't that foolish and when i put the new plugs in, it seems like the initial start was much smoother. I will have to keep an eye on my results the next several days and also reset the mpg monitor.

One thing that I found surprising was the lack of anti-seize on the factory plugs. That took the most torque to break each one loose that I have ever experienced for a plug on any of the 20+ vehicles that I have owned. Either that or the torque wrench operated by Otto was set to "manly" when they were initially installed.

DO NOT anti-seize your plugs, and if you do, adjust the torque appropriately. The engines are magnesuim block, not aluminum.

copper+magnesium+steel+electricity=bad

There's a reason that plugs are spec'd "DRY torque"

Vanos could easily be bad, they seem to last about 90k IF the oil is changed regularly (not every 10k), and then they are on borrowed time, but I've got new ones in my service records at ~50k from the dealer so... They can be cleaned, but the OE parts are cheap, so if your mileage is close, swap them out.

PhaseP · 03-19-2017, 03:28 PM

Plugs thread into the head which is aluminum. NGK the OEM at least for my year doesn't recommend using antisieze.
They have documentation on this at their website. They say the plugs have special plating on the threads which act like anti sieze

Eagle1oh7 · 03-19-2017, 06:07 PM

Quote:

Originally Posted by Atx328

My 2011 328i almost sounds like a diesel with a cold start in the morning. I am only getting about 20-21 mpg even with a good amount of highway driving thrown in. I should mention much of that is at 80-85 mph.

There are no codes being thrown, the rough start doesn't show up anytime later in the day and the engine runs super smooth. It does seem a bit sluggish having come from a Infiniti g35 previously but that was a larger and more powerful engine. Popping the auto over to sport mode provides a crisper response but then the mpg really goes south.

It's low mileage at 46k but I thought that I would try replacing the plugs first. Being an engineer I tend to try to only make one change at a time so I thought I would start with the plugs first to see what impact that has.

Is that a logical next step or am I being silly by not replacing the coils at the same time?

Anything else I should be considering?

At the mileage your plugs definitely need changing. I did mine around the same time and the engine came back stronger. Clean your MAF sensor as well. My MPG hasn't been good since moving to San Diego, but it's been better since installing AA headers.

Atx328 · 03-19-2017, 06:31 PM

wow - i think i ended up doing the right thing for the wrong reason.

I didn't use any anti-sieze on the new plugs but pretty much only because I didn't have any....

I did check the MAF when I swapped out the air filter and it was clean as a whistle.

I honestly would not have even changed out the filter element if I had just been checking it - but I had already purchased a new one so I thought it wasn't worth putting the old one back in for another 12K miles.

I was actually kind of surprised how clean the element was considering the amount of dust that had accumulated elsewhere on horizontal surfaces in the engine bay. There was even a small dust "wall" around the oil filler cap once I removed the plastic engine cover.

I look forward to driving the car more this week and I will post my finding back up next weekend.

03-05-2017, 08:44 AM	#1
Atx328 Private First Class 30 Rep 142 Posts Drives: 2011 328i sport Join Date: Aug 2016 Location: Austin tx iTrader: (0) Garage List 2013 BMW 328i [0.00] 2011 BMW 328 [0.00]	Rough start and poor mpg- are new plugs enough My 2011 328i almost sounds like a diesel with a cold start in the morning. I am only getting about 20-21 mpg even with a good amount of highway driving thrown in. I should mention much of that is at 80-85 mph. There are no codes being thrown, the rough start doesn't show up anytime later in the day and the engine runs super smooth. It does seem a bit sluggish having come from a Infiniti g35 previously but that was a larger and more powerful engine. Popping the auto over to sport mode provides a crisper response but then the mpg really goes south. It's low mileage at 46k but I thought that I would try replacing the plugs first. Being an engineer I tend to try to only make one change at a time so I thought I would start with the plugs first to see what impact that has. Is that a logical next step or am I being silly by not replacing the coils at the same time? Anything else I should be considering?
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03-05-2017, 09:21 AM	#2
AM330i First Lieutenant 90 Rep 386 Posts Drives: 08 535xi 11 328xi Join Date: Oct 2011 Location: Rochester, NY iTrader: (0) Garage List 2023 BMW M440 [0.00]	it's a very good possibility that your plugs are worn. I was having the same issue with my '11 328 around the same mileage. spark plug replacement interval is 60k so your pretty close anyway. __________________ Jb4/MHd BEF, XHD Stage 3 DCI, FTP Charge Pipe
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03-05-2017, 09:23 AM	#3
Flyboy161 Second Lieutenant 274 Rep 293 Posts Drives: 2008 E93 M3 Join Date: Apr 2014 Location: Perry, GA iTrader: (0) Garage List 2008 BMW M3 [0.00] 2012 BMW E92 335i [0.00]	Plugs, coils, air filter, oil change (if you're not sure of the last time it was done). Did you buy this car used? At a dealer or from a private individual? By "no codes are being thrown", do you mean you've read the codes with an OBD2 reader or have you used INPA or Carly to check the them? The former just reads generic codes the are often inaccurate in my experience. The latter will read error codes stored deep in the various modules and show specific problems. Rough cold start can be a caused by a number of things, one of which is gummed up VANOS solenoids that aren't advancing your cams properly. Some of these errors can show themselves in the modules without tripping the Service Engine Soon light.
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03-05-2017, 12:58 PM	#4
Atx328 Private First Class 30 Rep 142 Posts Drives: 2011 328i sport Join Date: Aug 2016 Location: Austin tx iTrader: (0) Garage List 2013 BMW 328i [0.00] 2011 BMW 328 [0.00]	Thanks for the clarification flyboy! I purchased the vehicle from a private party but they had all service done at BMW so it was relatively easy to pull a detailed history. I have already purchased the plugs and air filter and the oil change was recent. I would like to avoid doing the coils early if they don't actually have an impact. My previous daily driver was a mazdaspeed miata and I didn't have an issue tossing new parts at a problem when spark plus were $8 a set and coils were $40. With the obviously higher costs of BMW operations, I would like to avoid replacing parts that are working well. I was referring to codes present when the check engine light is lit. I have access to a really great local Indy so I will ask him to pull any subsystem type codes the next time I visit his shop (probably this week). I am interested in picking up a Carly as I strongly believe more data leads to better decisions. As a relative newby, will the tool work with my wife's N20 motor in her f30 as well?
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03-05-2017, 01:39 PM	#6
dannyhavok Lieutenant 133 Rep 514 Posts Drives: '11 E90 328xi 6MT Join Date: Jun 2014 Location: Victoria, BC iTrader: (0)	I had these exact symptoms recently when my eccentric shaft sensor was failing. I was getting about 15L/100KM when I normally get 10-12 in mixed driving. It would also occasionally stall on startup.
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03-05-2017, 02:39 PM	#7
AWSB328iM Captain 397 Rep 647 Posts Drives: 2011 E92 328i M-Sport 6MT Join Date: Nov 2016 Location: Memphis, TN iTrader: (0)	Change the plugs first. I just had issues with misfires on my car at 60k miles and the issue has gone away. Plugs were $56 shipped on eBay. Watch a YouTube video about changing the plugs and it should take you around a hour. Cold start idle has smoothed somewhat and mileage has increased around 1-1.5 mpg around town. Plug replacement: Plugs: https://www.ebay.com/itm/112316731791
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03-05-2017, 04:07 PM	#8
Flyboy161 Second Lieutenant 274 Rep 293 Posts Drives: 2008 E93 M3 Join Date: Apr 2014 Location: Perry, GA iTrader: (0) Garage List 2008 BMW M3 [0.00] 2012 BMW E92 335i [0.00]	I went ahead and uploaded almost all the documents I have from BMW University in a thread over in manuals. http://www.e90post.com/forums/showth...6#post21370206
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03-05-2017, 04:09 PM	#9
blackturbo Captain 59 Rep 645 Posts Drives: 335i Join Date: Jul 2013 Location: vancouver iTrader: (1)	Your on the right track. I would suggest plugs first. My mileage was changed when my Camshaft sensor(exhaust) was malfunctioning. I threw a check engine. Pulled the code, and replaced it. Mileage was back to normal. When I have time next week I'll be replacing the other Camshaft sensor (intake). If that intake sensor fails, you can't even start your car. Your probably looking at 80,000 miles to replace the sensors and they are relatively cheap. Just get the vdo ones, bmw oem just puts a stamp on them and unchanged. Good luck. Let us know if there's any change with the plugs.
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03-05-2017, 10:53 PM	#12
absentmathis Private 15 Rep 76 Posts Drives: 07 335 Join Date: Jan 2017 Location: Charlotte iTrader: (0)	Plugs are not going to change much of anything.
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03-06-2017, 12:36 AM	#14
TemjinX2 Major 521 Rep 1,485 Posts Drives: 2008 335xi e92 Join Date: Dec 2009 Location: Socal OC iTrader: (0)	The engine in the e9x series engines are pretty simple compared to todays car's, so i wouldn't worry. I agree, with everyone else, just take your time, read through some of the diy's and its pretty straight forward.
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03-06-2017, 02:34 AM	#15
ctuna Lieutenant General 1911 Rep 13,104 Posts Drives: 325xi 06 wagon MT Join Date: Jan 2010 Location: Santa Cruz, Ca iTrader: (0)	If it only happens on the first start of the day it could be a weak battery. Try putting a full charge on the battery to see if things change for the first start problem. http://www.e90post.com/forums/showthread.php?t=13504 electical e90 pdf http://www.google.com/url?sa=t&rct=j...,d.cGU&cad=rja http://www.google.com/url?sa=t&rct=j...85464276,d.cGU http://www.google.com/url?sa=t&rct=j...85464276,d.cGU these cars don't get that good a mileage in town freeway is pretty good. You could try reseting the adaptions . Last edited by ctuna; 03-06-2017 at 02:47 AM..
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03-18-2017, 01:08 PM	#16
Atx328 Private First Class 30 Rep 142 Posts Drives: 2011 328i sport Join Date: Aug 2016 Location: Austin tx iTrader: (0) Garage List 2013 BMW 328i [0.00] 2011 BMW 328 [0.00]	So I just got back from Vacation a few days ago so I wasn't able to find time to swap out my plugs until this morning. Plugs 3-6 looked pretty good but they definitely had a wider gap than the new ones. Plug 2 was almost at the recommend gap and then 1 was inbetween 2 and 3-6. If I was going to be cheap, it looks like I could have simply cleaned them up, regapped them to factory specs and run another 15K easily. However, I wasn't that foolish and when i put the new plugs in, it seems like the initial start was much smoother. I will have to keep an eye on my results the next several days and also reset the mpg monitor. One thing that I found surprising was the lack of anti-seize on the factory plugs. That took the most torque to break each one loose that I have ever experienced for a plug on any of the 20+ vehicles that I have owned. Either that or the torque wrench operated by Otto was set to "manly" when they were initially installed.
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03-19-2017, 10:56 AM	#17
Flyboy161 Second Lieutenant 274 Rep 293 Posts Drives: 2008 E93 M3 Join Date: Apr 2014 Location: Perry, GA iTrader: (0) Garage List 2008 BMW M3 [0.00] 2012 BMW E92 335i [0.00]	Great followup! Keep us posted.
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03-19-2017, 11:41 AM	#18
roundle EXPAT 65 Rep 889 Posts Drives: 18 VW GTI;18 CX9;11 E91 N52 Join Date: Apr 2010 Location: USA iTrader: (0)	The N52 likes plugs every 50K miles or so. Your coils are probably fine for another 50K miles. Might be worth pulling the VANOS solenoids out and, depending upon how they look, giving them a quick bath in brake cleaner. Might be interesting to post a good quality video with sound to help people understand the problem you are trying to solve. Are you getting a knocking sound? If yes, could be lifter related (but unlikely given that you have a 'new' N52 head).
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03-19-2017, 03:28 PM	#20
PhaseP Colonel 1007 Rep 2,108 Posts Drives: 325XI Join Date: May 2010 Location: Earth iTrader: (0)	Plugs thread into the head which is aluminum. NGK the OEM at least for my year doesn't recommend using antisieze. They have documentation on this at their website. They say the plugs have special plating on the threads which act like anti sieze
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03-19-2017, 06:31 PM	#22
Atx328 Private First Class 30 Rep 142 Posts Drives: 2011 328i sport Join Date: Aug 2016 Location: Austin tx iTrader: (0) Garage List 2013 BMW 328i [0.00] 2011 BMW 328 [0.00]	wow - i think i ended up doing the right thing for the wrong reason. I didn't use any anti-sieze on the new plugs but pretty much only because I didn't have any.... I did check the MAF when I swapped out the air filter and it was clean as a whistle. I honestly would not have even changed out the filter element if I had just been checking it - but I had already purchased a new one so I thought it wasn't worth putting the old one back in for another 12K miles. I was actually kind of surprised how clean the element was considering the amount of dust that had accumulated elsewhere on horizontal surfaces in the engine bay. There was even a small dust "wall" around the oil filler cap once I removed the plastic engine cover. I look forward to driving the car more this week and I will post my finding back up next weekend.
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