Engine Rough Start and Low MPG

stoweboarder720 · 05-30-2017, 11:32 PM

Hey guys, so I've been doing a lot of searching around the forum over the past couple days to try and diagnose what's going on with my 2011 e90 328xi. No check engine or other warning lights have popped up. I haven't had a chance to check for codes that may not show up on the check control/check engine display.

As of several weeks ago, I started noticing a drop off in my highway mileage. I used to average around 30 to 32 mpg (if I were babying it) on the highway at around 70-75 mph. I haven't changed my driving style at all either. Even when I wasn't being very kind on the highway it would drop to at most 28 mpg. Now, I'm seeing 25-26mpg and don't know why. I saw some people point to AC, however I haven't turned mine on yet this season so that isn't it.

Other symptoms include a pretty rough start. Once it's been idling for 10 seconds or so, rpms settle and then come down steadily as you'd expect, settling at a consistent 600 or so rpm. During start though, it's really anyone's guess how it'll behave. Sometimes it takes longer than usual to turn over and then revs high before settles (2k-ish). Other times it will start with really low revs and then cough and recover to above 1k. Point is, I've never had this problem before, starting has been consistent.

Lastly, its late May, so I was surprised to see small amounts of white smoke coming out the back, namely closer to start. I really don't think this is normal, even if its within 5 minutes of start. I've had the car for well over a year now and during warm weather there has never been the slightest bit of smoke after starting the car (save an initial puff from getting the engine to turn over).

So that pretty much covers all the symptoms. Now, the part I'm having difficulty with is what my best bet on diagnosis is, granted I will have more info regarding the matter this weekend when I can get under the hood.

Basically, I've found that it could be one of the following:

1. Mass Airflow Sensor
2. Eccentric Shaft Sensor
3. Spark Plugs
4. Camshaft Position Sensor(s)
5. Vanos Solenoids

This list is based off of solutions that others have found to similar sounding problems. I'm most inclined for it to be to spark plugs, simply because the car is at 62k and I haven't replaced them yet. I don't think its a coil since I had one fail about 4k ago and that caused the engine to turn into a simulated earthquake with absolutely zero power. The car still seems to have a good amount of power (maybe slightly less but I can't tell, haven't been able to take it on a spirited drive since this started). The only thing I kind of notice is that when getting it into first the RPMs seem to dip more than they have in the past despite similar throttle input. That's pretty much all I've got. Oh, and I'm gonna pull out the eccentric shaft sensor this weekend and check for any oil buildup, which if there is, would likely be the culprit. I will update as soon as that happens.

Sorry for the book but I hope the info can help diagnose the issue. If anyone has any ideas they are greatly appreciated. Thanks guys!

JuniorB · 05-31-2017, 03:10 AM

It sounds like you haven't pulled any codes, if it was a sensor, there would be a code showing,and rough idle. Clean your maf with maf cleaner, install a new air filter,and change the plugs. Your car will run much better just doing that, you can also pull the vanos solidnoids and clean them out, reinstall. Even a basic reader will pull codes on sensors that are bad. Although rare, check your fuel pressure to be on the safe side,but I'd lean to the maintenance items for tour bad fuel mileage .

stoweboarder720 · 05-31-2017, 07:43 AM

I haven't been able to read codes yet so I'm not sure, maybe there are some that don't show up in the form of a check engine light or warning on the trip computer, not quite sure. Either way, I will be reading them in the coming days. I agree with you though, I feel like if it were any of the sensors then either the check engine or a check control warning would pop up.

stoweboarder720 · 05-31-2017, 08:27 AM

If I replace the plugs, would it be worth it to just go ahead and replace coils at 62k despite the recommended interval being 100k?

e90dum · 06-01-2017, 06:36 AM

I remember my car didnt pop any codes. (Or maybe it did, but no ses) with my eccentric shaft sensor. LITERALLY my only clue was the car limited it's self to 6500 RPM. That was it. (And oil coming out of the plug. LOL)

e90dum · 06-01-2017, 06:41 AM

Quote:

Originally Posted by stoweboarder720

If I replace the plugs, would it be worth it to just go ahead and replace coils at 62k despite the recommended interval being 100k?

I replaced a coil from autozone for less than $18 bucks on the spot i'm sure they're cheaper for a kit online. I think your call, theyre easy to replace so it's not like your wasting your time by not doing it. I personally would throw my money at it to make sure that isn't the issue/part of it

stoweboarder720 · 06-05-2017, 07:53 AM

I'd be willing to do the coils at the same time. But I've heard that there can be increased risk from say using bosch OEM coils vs BMW (bosch) OE coils, something along the lines of quality control. Also I read somewhere that if you replace coils (and maybe plugs? can't remember) that the ignition timing needs to be check and re-coded? If someone can verify this here that'd be helpful, otherwise I'll just poke around the forum a bit.

Also, update (I would really appreciate any other suggestions!):
Car still starts pretty rough from time to time. Engine cranks for awhile before turning over, in the neighborhood of 2 to 3 seconds as opposed to the normal 3 or 4 cranks. There is some smoke coming from the tailpipe for 5 or so minutes after start still which is odd. Also, after the engine turns over RPMs often drop sharply (like down to 350 or 400) and then recover, I've never had this happen previously. It used to rev high (1000-1500) and then slowly settle down to a low RPM, never struggling to maintain RPM. While driving the engine runs really smoothly and doesn't feel down on power despite lower MPGs (seeing 26-27 highway vs the usual 31-32 and no my habits have not changed with regard to AC or route).

Once again, sorry for the book but I'm not really finding much on this issue and I don't want to start throwing big money at the car for things like the eccentric shaft sensor until I know what it is. I still have to clean out the air filter and check for oil in the shaft sensor and will update when I do. Sorry I've been delayed on that end, rain hasn't let up here and work has been hectic. Thanks again guys!

stoweboarder720 · 06-07-2017, 10:42 PM

Update:

So I pulled all the codes with INPA and got 2A31, 2A32, 2A37, and 2A33, which all are eccentric shaft sensor errors. I also got faults for engine turn off time and a fault with the tank ventilation solenoid valve, but I'm guessing those are tied to the faulty eccentric shaft sensor. I ordered a new eccentric shaft sensor from ECS (just the VDO one, not BMW, not worth twice the price for marginal increase in quality control). I also ordered a new valve cover gasket, valvetronic motor gasket, and eccentric shaft sensor gasket along with new spark plugs since I just passed 60k and it's time for new ones.

I'm still pretty terrified by all these horror stories about recalibrating valvetronic after removing the motor so any tips would be fantastic.

Just wanted to provide an update so anyone experiencing similar symptoms can get something out of the thread. I'll update again after the repairs and hopefully everything goes smoothly!

hassmaschine · 06-09-2017, 08:32 AM

you don't have to do anything special. I don't know what horror stories you're referring to, but most people have no clue how valvetronic works.

You do need to move the VVT motor to "service mode" before removing it from the valve cover. not doing this risks breaking the shaft off the end of the motor. basically you just turn a hex key until the tension of the eccentric shaft is off the motor.

When you put it all back together, I believe you just turn on the ignition without starting the car. the VVT system will calibrate itself. There's really nothing to do manually.

stoweboarder720 · 06-09-2017, 09:01 PM

So I just took apart all the engine covers and checked the eccentric shaft sensor. There was a slight amount of oil in it, like a very thin film over the sensor connector and small droplets around the outside of the female side of the connector. No pooling around the seal or in the connector like I've seen with some people. I searched around and haven't found anyone who's had a little bit of oil like this, though I'm assuming that the sensor can fail like any other part.

However, I still received all the codes regarding the eccentric shaft sensor specifically, such as 2a31, 2a32, 2a33, and 2a37. So, needless to say I'm at a bit of a loss. Could that little amount of oil cause it to fail or should I start looking for the problem elsewhere? I haven't read about any other component in the engine that results in the difficult cold starts and decreased mpg, short of maybe coils/plugs. But I'm confident it's neither of those because then the engine wouldn't be running smoothly after its warmed up for 30 seconds. The only other part would be the VANOS solenoids but I'm doubtful of that given that no codes concerning it were thrown and the engine idle is not rough at all once the car's been running.

I'm replacing the sensor tomorrow so if anyone has insight please let me know ASAP. Thanks guys!

hassmaschine · 06-10-2017, 06:46 AM

it's not that the oil is causing it to fail. It's probably cracked or seal has failed, so now oil is leaking through the sensor - it's a symptom of the bad sensor, not necessarily the cause.

stoweboarder720 · 06-10-2017, 09:20 PM

So I completed the sensor swap. Started it up and all the eccentric shaft sensor codes were gone. However, the engine started to smoke and the smoke had a very metallic smell and it ran a little rough. I shut it off immediately and rescanned. I have a cylinder misfire code though it doesn't specify the cylinder which would explain the rough idle (though the start was way smoother than before ironically, so the shaft sensor must've been bad). Anyway, the smoke really freaked me out. Though it was oil but the metallic smell threw me off. I used a lot of copper-based liquid gasket to hold the valve cover gasket in place during installation, so my best guess now is that this smoke/smell is it burning off? Does anyone have any ideas? Please help!

GRUESOM3 · 06-16-2017, 05:09 AM

I just had a wierd problem like this. Slight misfire only at idle (leading to believe that it's eccentric shaft sensor). No codes were thrown. While I was replacing spark plugs about 2 months ago, one of the coils plastic broke on the shaft and I put it back in worked fine for a while but I guess from heat it was missing just enough to cause a problem but no codes thrown.

I inspected eccentric shaft connector as per suggestion on this board and it was bone dry.

Replaced that one coil that I knew was missing a little plastic on shaft and problem solved.

Make a long story short, double check your coils.

Hope this helps.

05-30-2017, 11:32 PM	#1
stoweboarder720 Private 31 Rep 87 Posts Drives: '11 E92 335is Join Date: Mar 2016 Location: Seattle iTrader: (0)	Engine Rough Start and Low MPG Hey guys, so I've been doing a lot of searching around the forum over the past couple days to try and diagnose what's going on with my 2011 e90 328xi. No check engine or other warning lights have popped up. I haven't had a chance to check for codes that may not show up on the check control/check engine display. As of several weeks ago, I started noticing a drop off in my highway mileage. I used to average around 30 to 32 mpg (if I were babying it) on the highway at around 70-75 mph. I haven't changed my driving style at all either. Even when I wasn't being very kind on the highway it would drop to at most 28 mpg. Now, I'm seeing 25-26mpg and don't know why. I saw some people point to AC, however I haven't turned mine on yet this season so that isn't it. Other symptoms include a pretty rough start. Once it's been idling for 10 seconds or so, rpms settle and then come down steadily as you'd expect, settling at a consistent 600 or so rpm. During start though, it's really anyone's guess how it'll behave. Sometimes it takes longer than usual to turn over and then revs high before settles (2k-ish). Other times it will start with really low revs and then cough and recover to above 1k. Point is, I've never had this problem before, starting has been consistent. Lastly, its late May, so I was surprised to see small amounts of white smoke coming out the back, namely closer to start. I really don't think this is normal, even if its within 5 minutes of start. I've had the car for well over a year now and during warm weather there has never been the slightest bit of smoke after starting the car (save an initial puff from getting the engine to turn over). So that pretty much covers all the symptoms. Now, the part I'm having difficulty with is what my best bet on diagnosis is, granted I will have more info regarding the matter this weekend when I can get under the hood. Basically, I've found that it could be one of the following: 1. Mass Airflow Sensor 2. Eccentric Shaft Sensor 3. Spark Plugs 4. Camshaft Position Sensor(s) 5. Vanos Solenoids This list is based off of solutions that others have found to similar sounding problems. I'm most inclined for it to be to spark plugs, simply because the car is at 62k and I haven't replaced them yet. I don't think its a coil since I had one fail about 4k ago and that caused the engine to turn into a simulated earthquake with absolutely zero power. The car still seems to have a good amount of power (maybe slightly less but I can't tell, haven't been able to take it on a spirited drive since this started). The only thing I kind of notice is that when getting it into first the RPMs seem to dip more than they have in the past despite similar throttle input. That's pretty much all I've got. Oh, and I'm gonna pull out the eccentric shaft sensor this weekend and check for any oil buildup, which if there is, would likely be the culprit. I will update as soon as that happens. Sorry for the book but I hope the info can help diagnose the issue. If anyone has any ideas they are greatly appreciated. Thanks guys! Last edited by stoweboarder720; 06-07-2017 at 10:45 PM..
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05-31-2017, 03:10 AM	#2
JuniorB Major 185 Rep 1,017 Posts Drives: 07 e60 525 N54 Join Date: Mar 2016 Location: Rhode Island iTrader: (0)	It sounds like you haven't pulled any codes, if it was a sensor, there would be a code showing,and rough idle. Clean your maf with maf cleaner, install a new air filter,and change the plugs. Your car will run much better just doing that, you can also pull the vanos solidnoids and clean them out, reinstall. Even a basic reader will pull codes on sensors that are bad. Although rare, check your fuel pressure to be on the safe side,but I'd lean to the maintenance items for tour bad fuel mileage .
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05-31-2017, 07:43 AM	#3
stoweboarder720 Private 31 Rep 87 Posts Drives: '11 E92 335is Join Date: Mar 2016 Location: Seattle iTrader: (0)	I haven't been able to read codes yet so I'm not sure, maybe there are some that don't show up in the form of a check engine light or warning on the trip computer, not quite sure. Either way, I will be reading them in the coming days. I agree with you though, I feel like if it were any of the sensors then either the check engine or a check control warning would pop up.
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05-31-2017, 08:27 AM	#4
stoweboarder720 Private 31 Rep 87 Posts Drives: '11 E92 335is Join Date: Mar 2016 Location: Seattle iTrader: (0)	If I replace the plugs, would it be worth it to just go ahead and replace coils at 62k despite the recommended interval being 100k? __________________ Cars: '11 E92 335is (Enter Boostman) '11 E90 328i xDrive [SOLD]
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06-01-2017, 06:36 AM	#5
e90dum Second Lieutenant 59 Rep 275 Posts Drives: E90 LCI 328i manual Join Date: Dec 2015 Location: East coast US iTrader: (0)	I remember my car didnt pop any codes. (Or maybe it did, but no ses) with my eccentric shaft sensor. LITERALLY my only clue was the car limited it's self to 6500 RPM. That was it. (And oil coming out of the plug. LOL)
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06-05-2017, 07:53 AM	#7
stoweboarder720 Private 31 Rep 87 Posts Drives: '11 E92 335is Join Date: Mar 2016 Location: Seattle iTrader: (0)	I'd be willing to do the coils at the same time. But I've heard that there can be increased risk from say using bosch OEM coils vs BMW (bosch) OE coils, something along the lines of quality control. Also I read somewhere that if you replace coils (and maybe plugs? can't remember) that the ignition timing needs to be check and re-coded? If someone can verify this here that'd be helpful, otherwise I'll just poke around the forum a bit. Also, update (I would really appreciate any other suggestions!): Car still starts pretty rough from time to time. Engine cranks for awhile before turning over, in the neighborhood of 2 to 3 seconds as opposed to the normal 3 or 4 cranks. There is some smoke coming from the tailpipe for 5 or so minutes after start still which is odd. Also, after the engine turns over RPMs often drop sharply (like down to 350 or 400) and then recover, I've never had this happen previously. It used to rev high (1000-1500) and then slowly settle down to a low RPM, never struggling to maintain RPM. While driving the engine runs really smoothly and doesn't feel down on power despite lower MPGs (seeing 26-27 highway vs the usual 31-32 and no my habits have not changed with regard to AC or route). Once again, sorry for the book but I'm not really finding much on this issue and I don't want to start throwing big money at the car for things like the eccentric shaft sensor until I know what it is. I still have to clean out the air filter and check for oil in the shaft sensor and will update when I do. Sorry I've been delayed on that end, rain hasn't let up here and work has been hectic. Thanks again guys!
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06-07-2017, 10:42 PM	#8
stoweboarder720 Private 31 Rep 87 Posts Drives: '11 E92 335is Join Date: Mar 2016 Location: Seattle iTrader: (0)	Update: So I pulled all the codes with INPA and got 2A31, 2A32, 2A37, and 2A33, which all are eccentric shaft sensor errors. I also got faults for engine turn off time and a fault with the tank ventilation solenoid valve, but I'm guessing those are tied to the faulty eccentric shaft sensor. I ordered a new eccentric shaft sensor from ECS (just the VDO one, not BMW, not worth twice the price for marginal increase in quality control). I also ordered a new valve cover gasket, valvetronic motor gasket, and eccentric shaft sensor gasket along with new spark plugs since I just passed 60k and it's time for new ones. I'm still pretty terrified by all these horror stories about recalibrating valvetronic after removing the motor so any tips would be fantastic. Just wanted to provide an update so anyone experiencing similar symptoms can get something out of the thread. I'll update again after the repairs and hopefully everything goes smoothly!
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06-09-2017, 08:32 AM	#9
hassmaschine Major General 3966 Rep 7,215 Posts Drives: "NBO" 330i Join Date: Jun 2014 Location: earth iTrader: (0)	you don't have to do anything special. I don't know what horror stories you're referring to, but most people have no clue how valvetronic works. You do need to move the VVT motor to "service mode" before removing it from the valve cover. not doing this risks breaking the shaft off the end of the motor. basically you just turn a hex key until the tension of the eccentric shaft is off the motor. When you put it all back together, I believe you just turn on the ignition without starting the car. the VVT system will calibrate itself. There's really nothing to do manually.
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06-09-2017, 09:01 PM	#10
stoweboarder720 Private 31 Rep 87 Posts Drives: '11 E92 335is Join Date: Mar 2016 Location: Seattle iTrader: (0)	Confusion So I just took apart all the engine covers and checked the eccentric shaft sensor. There was a slight amount of oil in it, like a very thin film over the sensor connector and small droplets around the outside of the female side of the connector. No pooling around the seal or in the connector like I've seen with some people. I searched around and haven't found anyone who's had a little bit of oil like this, though I'm assuming that the sensor can fail like any other part. However, I still received all the codes regarding the eccentric shaft sensor specifically, such as 2a31, 2a32, 2a33, and 2a37. So, needless to say I'm at a bit of a loss. Could that little amount of oil cause it to fail or should I start looking for the problem elsewhere? I haven't read about any other component in the engine that results in the difficult cold starts and decreased mpg, short of maybe coils/plugs. But I'm confident it's neither of those because then the engine wouldn't be running smoothly after its warmed up for 30 seconds. The only other part would be the VANOS solenoids but I'm doubtful of that given that no codes concerning it were thrown and the engine idle is not rough at all once the car's been running. I'm replacing the sensor tomorrow so if anyone has insight please let me know ASAP. Thanks guys!
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06-10-2017, 06:46 AM	#11
hassmaschine Major General 3966 Rep 7,215 Posts Drives: "NBO" 330i Join Date: Jun 2014 Location: earth iTrader: (0)	it's not that the oil is causing it to fail. It's probably cracked or seal has failed, so now oil is leaking through the sensor - it's a symptom of the bad sensor, not necessarily the cause.
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06-10-2017, 09:20 PM	#12
stoweboarder720 Private 31 Rep 87 Posts Drives: '11 E92 335is Join Date: Mar 2016 Location: Seattle iTrader: (0)	Help! So I completed the sensor swap. Started it up and all the eccentric shaft sensor codes were gone. However, the engine started to smoke and the smoke had a very metallic smell and it ran a little rough. I shut it off immediately and rescanned. I have a cylinder misfire code though it doesn't specify the cylinder which would explain the rough idle (though the start was way smoother than before ironically, so the shaft sensor must've been bad). Anyway, the smoke really freaked me out. Though it was oil but the metallic smell threw me off. I used a lot of copper-based liquid gasket to hold the valve cover gasket in place during installation, so my best guess now is that this smoke/smell is it burning off? Does anyone have any ideas? Please help!
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06-16-2017, 05:09 AM	#13
GRUESOM3 Major 1092 Rep 1,318 Posts Drives: 3 NA cars and 1 Turbo car Join Date: Jan 2013 Location: NJ iTrader: (4)	I just had a wierd problem like this. Slight misfire only at idle (leading to believe that it's eccentric shaft sensor). No codes were thrown. While I was replacing spark plugs about 2 months ago, one of the coils plastic broke on the shaft and I put it back in worked fine for a while but I guess from heat it was missing just enough to cause a problem but no codes thrown. I inspected eccentric shaft connector as per suggestion on this board and it was bone dry. Replaced that one coil that I knew was missing a little plastic on shaft and problem solved. Make a long story short, double check your coils. Hope this helps.
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