M5POST
BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read

Go Back   M5POST - BMW M5 Forum > F10 M5 Forum > BMW M5 (F10) General Forum

Post Reply
 
Thread Tools Search this Thread
      08-05-2020, 10:14 PM   #1
lior
New Member
2
Rep
13
Posts

Drives: 2013 M6 grand coupe
Join Date: May 2020
Location: Republic of georgia

iTrader: (0)

unstable RPM on Idle and acceleration

Hello All.
Firstly i would like to explain that there is no bmw center where i live so i would like if anyone can help me diagnose some issues.

I just recently bought an M6 GC 2013 with 55k KM [ about 32-4k miles], it idles\cold start\warm start very unstable [100-200] rpm difference mainly and it can sometimes surprise with a jump of 500 rpm.

when accelerating hard i am pretty sure that the power delivery is not smooth, at the beginning i thought it may be just bad tires or traction control kicking in to stop the acceleration from happening now that i am a little bit more used to the car driving i notice that and it worries me.

Recently [ few days ago ] i was revving the car in my underground parking just to have fun with it but i notice that there is a loud bang from the exhaust when you rev to about 3-4k rpm and put your foot of the pedal.

i would upload a sound video a little bit later.

the gearbox sometimes slams a gear on slow speeds [ usually gears 1-2-3 ] on traffic its not that harsh gearing but noticeable , i never drove a DCT before so im wondering if it is normal? and if not i know there is a sequence in bmw cars that i can do to change the gearbox driving and reset it to default [ the one with the gas pedal when car is off etc ] do you think it will help?

Thanks for all the help guys!

P.S i know there is a forum for M6 but it is kind of dead, would appreciate if the post will remain here since M5-M6 basically is the same car.

Last edited by lior; 08-07-2020 at 05:16 AM..
Appreciate 0
      08-05-2020, 10:38 PM   #2
Smurfzilla
Private First Class
22
Rep
150
Posts

Drives: E90 335i
Join Date: Jun 2016
Location: Raleigh

iTrader: (0)

Welcome to the board (I'm a fairly new owner still myself). The unstable idle and non linear acceleration could be bad plugs. i had a similar issue with my evo and found out plug 3 was fouled out. It made the car act crazy on acceleration and on cold starts/idle.

As for the trans.....I find that if you are decelerating and you gear down manually (coming to a stop light) and then try to accelerate quickly without changing gears (light turns green on you and you wernt anticipating it) it will cause my passengers head to hit the head rest violently if they arent ready for it. This only seems to happen when the trans is in the slowest mode (efficient), does this happen in all modes (sport and sport+ as well)?
Appreciate 0
      08-05-2020, 10:45 PM   #3
lior
New Member
2
Rep
13
Posts

Drives: 2013 M6 grand coupe
Join Date: May 2020
Location: Republic of georgia

iTrader: (0)

Quote:
Originally Posted by Smurfzilla View Post
Welcome to the board (I'm a fairly new owner still myself). The unstable idle and non linear acceleration could be bad plugs. i had a similar issue with my evo and found out plug 3 was fouled out. It made the car act crazy on acceleration and on cold starts/idle.

As for the trans.....I find that if you are decelerating and you gear down manually (coming to a stop light) and then try to accelerate quickly without changing gears (light turns green on you and you wernt anticipating it) it will cause my passengers head to hit the head rest violently if they arent ready for it. This only seems to happen when the trans is in the slowest mode (efficient), does this happen in all modes (sport and sport+ as well)?
i thought about plugs myself but i wanted to get other opinions on the matter.
since there is no bmw center in this country i need to order all the parts myself, Any idea what king of spark plugs i should put? i literally have no idea.

About the gearbox, I know what you mean but this is not what i meant. what you are talking about is completely normal. i was referring to the gearbox slamming the gear into drive and you can feel it shifting rough [there is also a small thump like sound but its really not that bad ].
Appreciate 0
      08-06-2020, 04:41 AM   #4
Craze
Captain
161
Rep
687
Posts

Drives: M5 E60, M5 F10, X5 50i
Join Date: Oct 2017
Location: Australia

iTrader: (0)

Do u have your foot on the brake going from n to drive??
Appreciate 0
      08-06-2020, 06:39 AM   #5
lior
New Member
2
Rep
13
Posts

Drives: 2013 M6 grand coupe
Join Date: May 2020
Location: Republic of georgia

iTrader: (0)

Quote:
Originally Posted by Craze View Post
Do u have your foot on the brake going from n to drive??
Yes at all times.
Appreciate 0
      08-06-2020, 06:42 AM   #6
technician117
Captain
United_States
251
Rep
606
Posts

Drives: 2000 M5, 2001 M5, 2013 M5 6MT
Join Date: Jul 2018
Location: Buffalo

iTrader: (1)

Garage List
1990 BMW M5  [0.00]
2000 BMW M5  [0.00]
2013 BMW M5  [0.00]
Start with the engine trouble before you waste time on transmission problems that may not exist. A stumbling engine can cause a lot of weird feelings in the car.

Spark plugs are a good first step. Do some basic searching on this forum for all the information you will need. If new and properly gapped plugs don't solve the issue, we can look deeper into other common fault areas.

Do you have access to a good code reader? If you're forced to work on everything yourself, I highly recommend you look into getting a copy of ISTA+ software to download on a laptop and buy a cable to go with it. This BMW program allows you to pull the BMW specific codes and makes diagnosis a bit easier overall.
Appreciate 0
      08-06-2020, 10:49 PM   #7
lior
New Member
2
Rep
13
Posts

Drives: 2013 M6 grand coupe
Join Date: May 2020
Location: Republic of georgia

iTrader: (0)

Quote:
Originally Posted by technician117 View Post
Start with the engine trouble before you waste time on transmission problems that may not exist. A stumbling engine can cause a lot of weird feelings in the car.

Spark plugs are a good first step. Do some basic searching on this forum for all the information you will need. If new and properly gapped plugs don't solve the issue, we can look deeper into other common fault areas.

Do you have access to a good code reader? If you're forced to work on everything yourself, I highly recommend you look into getting a copy of ISTA+ software to download on a laptop and buy a cable to go with it. This BMW program allows you to pull the BMW specific codes and makes diagnosis a bit easier overall.
thanks for your reply, however You have to understand that i can not really start with one problem and move on to the next one. i kinda need to diagnose everything at one occasion because i need to order parts from the US and that takes time.
no point waiting a month for spark plugs to arrive and then wait another month for something i can do now.

I will definitely get the code scanner. sadly it will only arrive in 3-4 weeks.

by this point its clear that everyone including myself thinks that the unstable idling is caused by the spark plugs and ignition coils.

Any other ideas about the rest of the stuff i wrote?

Appreciate your help.
Appreciate 0
      08-08-2020, 05:15 AM   #8
Mr. M6
Lieutenant
Mr. M6's Avatar
149
Rep
477
Posts

Drives: M6
Join Date: Jan 2018
Location: Bahrain

iTrader: (0)

Garage List
2014 BMW M6 F06  [9.25]
mods?

check your pre O2 sensors and MAF sensors, good luck
__________________
Appreciate 0
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -5. The time now is 04:35 PM.




m5post
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST