Z4-forum.com

Hi All,

Might be nothing but over the past few weeks I have noticed that occasionally the idle on my car will rise from 500rpm to around 900rpm momentarily, literally just a gentle 'rev up' and back to idle. Never happens when its warm though.
Car is a 2009 23i with nearly 80k on the clock, full history, drives like a dream..

Any ideas chaps??

Does this just happen first thing from cold after leaving overnight?

It happens irregularly, up until the oil has reached 70 deg then it behaves itself. It does not do it every time it idles and not more than twice on each idle.
If all that makes sense?
I am thinking injectors....

Hmmm, maybe but it's not classic injector symptoms. It's perhaps worth having a little spray around the engine with damp start to see if the revs rise to eliminate an air leak somewhere.

Maybe someone else with a 23i could comment if they ever get the same? I have known other cars do this to a lesser degree when the engine is loaded with things like the air con compressor kicking in.

I don’t have the answer but the 23i I had displayed exactly the same symptoms. It was still the same when I traded it in last year. I did report it to the local BMW dealer when taking it to be serviced but they said they couldn’t find anything wrong with it.

ph001 wrote: ↑Tue Oct 31, 2017 12:46 am Hmmm, maybe but it's not classic injector symptoms. It's perhaps worth having a little spray around the engine with damp start to see if the revs rise to eliminate an air leak somewhere.

Maybe someone else with a 23i could comment if they ever get the same? I have known other cars do this to a lesser degree when the engine is loaded with things like the air con compressor kicking in.

I rarely use the AC, last long trip I picked a long flat straight, set the instantaneous mpg display and watched the mpg as i switched it on and off. 10 MPG DIFFERENCE!!!!!!, that is over 35% less mpg or another £40 on my fuel bill for the trip each way!!!!

OK, got a fault code this morning, read from Carly is the following;

Note the mileages, second fault is the one that triggered todays yellow light.
Had a slight ticking in the head at times when cold as well, any ideas chaps??

Faultcode: (0x2A98) Crankshaft - inlet camshaft, correlation
Faultset 1:
(appeared at: 126048.0km)
(Engine) - oil temperature:
33.00 °C
engine status:
3.00 0-n
Engine speed:
1280.00 rpm
Voltage cl. 87:
14.73 V

Faultcode: (0x2A82) Intake Vanos variable cam control test
Faultset 1:
(appeared at: 128240.0km)
Engine speed:
1760.00 rpm
engine temperature:
89.25 °C
camshaft intake:
66.75 °CRK
Camshaft intake setpoint:
60.00 °CRK

Well from that you would have to suspect either camshaft position sensor or a Vanos issue (probably solenoid). Neither are particularly expensive or difficult to replace on the N52B25 engine. Ducklakeview is your man for Vanos work at sensible money.

Crank case breather valve has been known to cause strange issues as well.. https://www.youtube.com/watch?v=cIRPtA93wxw

Yup, looks like a lack of correlation between "requested" intake cam position and "actual" which could be caused by the solenoid not opening/closing correctly.. It's possible to "test" the actuations more thoroughly on my Launch, whereas Carly just gives yo the codes.

Mike

This little guide looks useful for the cam position sensor, but I suspect vanos solenoid is more likely.... http://www.pelicanparts.com/BMW/techart ... lacing.htm

Ducklakeview wrote: ↑Wed Nov 01, 2017 1:02 pm Yup, looks like a lack of correlation between "requested" intake cam position and "actual" which could be caused by the solenoid not opening/closing correctly.. It's possible to "test" the actuations more thoroughly on my Launch, whereas Carly just gives yo the codes.

Mike

Hi Mike, What is 'my launch?'..

mcbutler wrote: ↑Wed Nov 01, 2017 3:07 pm

Ducklakeview wrote: ↑Wed Nov 01, 2017 1:02 pm Yup, looks like a lack of correlation between "requested" intake cam position and "actual" which could be caused by the solenoid not opening/closing correctly.. It's possible to "test" the actuations more thoroughly on my Launch, whereas Carly just gives yo the codes.

Mike

Hi Mike, What is 'my launch?'..

That..

Mike

Ducklakeview wrote: ↑Wed Nov 01, 2017 3:16 pm

mcbutler wrote: ↑Wed Nov 01, 2017 3:07 pm

Ducklakeview wrote: ↑Wed Nov 01, 2017 1:02 pm Yup, looks like a lack of correlation between "requested" intake cam position and "actual" which could be caused by the solenoid not opening/closing correctly.. It's possible to "test" the actuations more thoroughly on my Launch, whereas Carly just gives yo the codes.

Mike

Hi Mike, What is 'my launch?'..

That..

Mike

Ah HAH, a bit out of my price range me thinks..

I am taking it to a local indy next friday, I have a warranty direct cover on it, lets see how they take the news.... Badly I am thinking.
Later today I will do the crank breather test, see how hard its 'sucking'....

Thanks for your help.

Not the breather, no vaccum at all in the crankcase.

The two Vanos solenoids are simple enough to whip out and give a good clean through with carb cleaner. Access is a bit tighter on the Z4 than on other N52 engines but doable.... http://www.zpost.com/forums/showthread.php?t=1022260

and this...
viewtopic.php?t=84789