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Old 04-18-2017, 09:02 AM   #1
lemoose
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Join Date: Feb 2017
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Shuddering at low RPM

I first noticed the issue about a week ago. At low rpms (lightly pressing the gas), the car shudders and doesnt deliver much power. At higher RPMs, it smooths itself out. I want to say that when I first noticed it, my gas tank was rather low. Today, my gas tank is low again and it is acting up again. SEL has been one since before I experienced this issue, however, it has been for exhaust O2 sensors. I will check it again today to see if theres any new codes that pop up.

Car is an 02 SMG M3 with 130k miles. Any and all help much appreciated!

Last edited by lemoose; 04-18-2017 at 09:02 AM.
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Old 04-18-2017, 09:37 AM   #2
lemoose
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P0174 with misfire codes for cylinders 1-6 and P0300 =/
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Old 04-18-2017, 10:00 AM   #3
dad
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Quote:
Originally Posted by lemoose View Post
P0174 with misfire codes for cylinders 1-6 and P0300 =/
you probably have a vacuum leak somewhere. there's a great thread dedicated to random misfires.
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Old 04-18-2017, 11:15 AM   #4
SSchwab
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Have you ever replaced the fuel pump?
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Old 04-18-2017, 11:37 AM   #5
lemoose
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Quote:
Originally Posted by dad View Post
you probably have a vacuum leak somewhere. there's a great thread dedicated to random misfires.
I believe I have found it. I'll inspect the DISA,CCV and intake boot this afternoon.

Quote:
Originally Posted by SSchwab View Post
Have you ever replaced the fuel pump?
I don't believe this has ever been performed. But I've considered this as a possible cause too.
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Old 04-18-2017, 11:42 AM   #6
SSchwab
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Idle problems when the gas level is low are signs of a failing fuel pump.
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Old 04-19-2017, 08:45 AM   #7
lemoose
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Quote:
Originally Posted by dad View Post
you probably have a vacuum leak somewhere. there's a great thread dedicated to random misfires.
Okay, so I tried a smoke leak detection and there appears to be no leaks.

Quote:
Originally Posted by SSchwab View Post
Idle problems when the gas level is low are signs of a failing fuel pump.
To this end, I did fill up yesterday and the problem actually persists.

I've noticed that the shuddering/ poor throttle response occurs with light to moderate presses of the pedal. At or near WOT, there is no shuddering and the throttle responds fine. I will try replacing both precat sensors as one is not responding and the other is slow.
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Old 04-19-2017, 01:39 PM   #8
jfoj
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M3's have far fewer possible sources for vacuum leaks.

M car fuel pumps run at a higher pressure and experience has shown they do soft fail and can loose pressure and volume causing driveability problems.

I personally would consider the fuel pump on a short list at this age/mileage.

Pre-cat O2 sensors are overdue for replacement, they should be replaced at 100k miles, they can get lazy or fail before this or they can sometimes last longer, but BMW recommends they be replaced at 100k miles. But since you had a P0174 code, then at least the Bank #2 sensor is working well enough to detect a Lean condition.

But in the interim you need to gather Freeze Frame and Fuel Trim data.

If you have a smart phone or table, get an OBDII App and interface so you can read the codes along with Live/Realtime or Freeze Frame data then you will know exactly what is going on with the engine fuel management system.

The OBDFusion App and proper VeePeak interface from Amazon are less than $30 for both for iProducts, less than $20 for both for Android

OBDFusion for Android is is $3.99.

https://www.amazon.com/Veepeak-Bluet...peak+bluetooth

OBDFusion, for the iProducts it is $9.99.

For iProducts you NEED a Wifi adapter or LE Bluetooth adapter which are more expensive and VeePeak does not offer these yet..

iProducts requires Wifi - https://www.amazon.com/dp/B00WPW6BAE...ywords=veepeak
__________________
Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temp, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose temp switch O-ring - BMW #13621743299
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Old 04-20-2017, 11:52 AM   #9
lemoose
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Quote:
Originally Posted by jfoj View Post
M3's have far fewer possible sources for vacuum leaks.

M car fuel pumps run at a higher pressure and experience has shown they do soft fail and can loose pressure and volume causing driveability problems.

I personally would consider the fuel pump on a short list at this age/mileage.

Pre-cat O2 sensors are overdue for replacement, they should be replaced at 100k miles, they can get lazy or fail before this or they can sometimes last longer, but BMW recommends they be replaced at 100k miles. But since you had a P0174 code, then at least the Bank #2 sensor is working well enough to detect a Lean condition.

But in the interim you need to gather Freeze Frame and Fuel Trim data.

If you have a smart phone or table, get an OBDII App and interface so you can read the codes along with Live/Realtime or Freeze Frame data then you will know exactly what is going on with the engine fuel management system.

The OBDFusion App and proper VeePeak interface from Amazon are less than $30 for both for iProducts, less than $20 for both for Android

OBDFusion for Android is is $3.99.

https://www.amazon.com/Veepeak-Bluet...peak+bluetooth

OBDFusion, for the iProducts it is $9.99.

For iProducts you NEED a Wifi adapter or LE Bluetooth adapter which are more expensive and VeePeak does not offer these yet..

iProducts requires Wifi - https://www.amazon.com/dp/B00WPW6BAE...ywords=veepeak
Thanks for the app suggestions. My sensors along with my OBD Wifi tool are arriving today. I'll update you with the Freeze Frame and Fuel Trim data. I did notice yesterday that it seems like the Cyl 2 coil is not making adequate contact, and after wiggling it in more securely, the car seems to be behaving better. However, i do notice a worrysome rattle from the vanos area that kicks in at 3k and dies off at lower/higher rpms. =/

Last edited by lemoose; 04-20-2017 at 11:53 AM.
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