The engine of My 2008 e85 z4 works unstably only in idle speed of D or R. It was going well in other situation. The speed will drop only a second and become normal again.(I have changed spark plug and fuel filter already but it did not work) Has someone met the same situation and can give me some advice?Thanks a lot!!
Help!Engine works unstably only in Idle speed
- Thread starter se4y
- Start date
Hi and welcome 
What engine and mileage do you have, that would be good for starters?
Does it do it more when engine is cold or hot?
I had a similar issue with rough and uneven idling on my manual 3.0si though, however mine kept tripping an engine management light at odd intervals, there was also an error code recorded as well. My fault was intermittent and only effected the idle on occasions which was a real pain. Do you have a code reader to check if yours has any error codes recorded?
This was my thread which detailed my 6 month journey http://www.z4-forum.com/forum/viewtopic.php?f=3&t=46501
Hopefully another more mechanically minded member will be able to offer you some further advice.
What engine and mileage do you have, that would be good for starters?
Does it do it more when engine is cold or hot?
I had a similar issue with rough and uneven idling on my manual 3.0si though, however mine kept tripping an engine management light at odd intervals, there was also an error code recorded as well. My fault was intermittent and only effected the idle on occasions which was a real pain. Do you have a code reader to check if yours has any error codes recorded?
This was my thread which detailed my 6 month journey http://www.z4-forum.com/forum/viewtopic.php?f=3&t=46501
Hopefully another more mechanically minded member will be able to offer you some further advice.
Thank you !!Swiftly said:Hi and welcome
What engine and mileage do you have, that would be good for starters?
Does it do it more when engine is cold or hot?
I had a similar issue with rough and uneven idling on my manual 3.0si though, however mine kept tripping an engine management light at odd intervals, there was also an error code recorded as well. My fault was intermittent and only effected the idle on occasions which was a real pain. Do you have a code reader to check if yours has any error codes recorded?
This was my thread which detailed my 6 month journey http://www.z4-forum.com/forum/viewtopic.php?f=3&t=46501
Hopefully another more mechanically minded member will be able to offer you some further advice.
I have read your thread. It seems we are in the same boat! It disapeared only for a month when I have tried Engine Oil Additive But now it comes back again.
I will clean the carbon deposit of engine by dealer or change airflow meter
so we can keep in touch !(The dealer told me to driver in manual 3 at 3000r 10 minutes to clean the carbon deposit but it still didnot work)
Does it mean you have changed the airflow meter and have solved the problem?mac27040 said:
I will try. (I have changed it one time from another N52 engine to test if my engine will drop down when it was in D idling. It was same ,so I gave up.)
thanks a lot for you advice
!!Does it mean you have changed the airflow meter and have solved the problem?mac27040 said:
(I have change it from another N52 engine and test if my engine will drop down when it is in D idling cause new style engine will not.It looks as same as mine. so I change back.)
I will try to change a new airflow meter. Thanks a lot!!!
Found this
N52 engine the latest 6-cylinder gasoline engine design, in the US. While there are some specific rough idle issues for the M54 and M56 6-cylinder engines (such as the DISA, or Adjuster Unit, on the intake manifold), I did not find much on historical rough idle problems for the N52 engine. I did, however, find a BMW service bulletin related to rough idle issues on the N52 engine. The bulletin basically talks about carbon deposits in the intake tract, on the injector tip and in the combustion chambers. The bulletin is not unique to the N52 engine. It also covers the N51, M54, S54, M56 and N62 engines (basically all of the late model low emissions engines).
If the car is under warranty, I would suggest that you ask the dealership to address this bulletin. If the car is out of warranty, I would suggest that you apply some DIY, at this point.
I’d recommend an application of the Lubro-Moly Jectron (fuel system & injector cleaner) and the Ventil Sauber (carbon cleaner) as a first course of action. If your rough idle is due to carbon build-up, the use of these products will improve the idle as the carbon is dissolved and removed. Use one can of each product in alternating tanks of fuel. I’d go through two cans of each (four tanks of fuel). Give it a couple thousand miles and then see if the idle is improving.
BMW Service Bulletin SI B 13 01 07:
BMW Rough Idle bulletin
N52 engine the latest 6-cylinder gasoline engine design, in the US. While there are some specific rough idle issues for the M54 and M56 6-cylinder engines (such as the DISA, or Adjuster Unit, on the intake manifold), I did not find much on historical rough idle problems for the N52 engine. I did, however, find a BMW service bulletin related to rough idle issues on the N52 engine. The bulletin basically talks about carbon deposits in the intake tract, on the injector tip and in the combustion chambers. The bulletin is not unique to the N52 engine. It also covers the N51, M54, S54, M56 and N62 engines (basically all of the late model low emissions engines).
If the car is under warranty, I would suggest that you ask the dealership to address this bulletin. If the car is out of warranty, I would suggest that you apply some DIY, at this point.
I’d recommend an application of the Lubro-Moly Jectron (fuel system & injector cleaner) and the Ventil Sauber (carbon cleaner) as a first course of action. If your rough idle is due to carbon build-up, the use of these products will improve the idle as the carbon is dissolved and removed. Use one can of each product in alternating tanks of fuel. I’d go through two cans of each (four tanks of fuel). Give it a couple thousand miles and then see if the idle is improving.
BMW Service Bulletin SI B 13 01 07:
BMW Rough Idle bulletin
Try simply cleaning the airflow meter before resorting to replacement.se4y said:Does it mean you have changed the airflow meter and have solved the problem?mac27040 said:
(I have change it from another N52 engine and test if my engine will drop down when it is in D idling cause new style engine will not.It looks as same as mine. so I change back.)
I will try to change a new airflow meter. Thanks a lot!!!
Did you get the "Service Engine Soon" malfunction indicator light? If so, what are the codes read?
Inspect carefully for any air leakage, in particular the intake side. Apparently, per Swiftly's experience, the exhaust between engine and cats should be inspected as well. For lack of any solid diagnostic information, I'm inclined to suspect one or more of the coil packs are acting up.
se4y said:Thank you !!Swiftly said:Hi and welcome
What engine and mileage do you have, that would be good for starters?
Does it do it more when engine is cold or hot?
I had a similar issue with rough and uneven idling on my manual 3.0si though, however mine kept tripping an engine management light at odd intervals, there was also an error code recorded as well. My fault was intermittent and only effected the idle on occasions which was a real pain. Do you have a code reader to check if yours has any error codes recorded?
This was my thread which detailed my 6 month journey http://www.z4-forum.com/forum/viewtopic.php?f=3&t=46501
Hopefully another more mechanically minded member will be able to offer you some further advice.
I have read your thread. It seems we
are in the same boat! It disapeared only for a month when I have tried Engine Oil Additive But now it comes back again.
I will clean the carbon deposit of engine by dealer or change airflow meter
so we can keep in touch !(The dealer told me to driver in manual 3 at 3000r 10 minutes to clean the carbon deposit but it still didnot work)
My fault was finally fixed by the dealer when they replaced the fuel tank vent/breather valve.