idle stumble on start - then OK - ...UPDATE - FIXED!

[Migizi]

2006 Z4 E85 3.0si
EDIT (add)---Engine is an N52

I have done lots to this car since I purchased it in January, she is now road worthy (IMO) - including new plugs and coils, gaskets, alignment, tires, and cosmetics ...

I do however have an issue that is bothersome, perhaps someone on this forum has experienced it or knows the likely cause?....

Warm or cold...every time I start it, the idle stumbles up and down 50/75 rpm of the target idle RPM. this lasts for 5-15 seconds then settles in and all is great till next time I start it.

DISA?
VANOS?
Bueller?

 

[Smartbear]

Add eccentric cam sensor to that list, you can unplug it to see if the idle becomes steady :?
Rob

 

[ph001]

50 - 75rpm sounds pretty minor and if it only lasts 10 seconds or so I’m not sure I would be worrying about it. I think they all do that to some degree. I suppose you could take the vanos solenoids out and give them a good clean just because it’s easy to do but I don’t think I would be stripping eccentric shaft sensors and valvetronic motors apart at this stage.

 

[thecookie125]

Mine does this too but usually only on warm start, clears after about 10 seconds or so. Going to start by cleaning the vanos solenoids.

 

[Jameszy]

Mine does this too, 3.0si, usually on a cold start. Lasts about 10 seconds. Not been an issue so far, but might consider looking at VANOS solenoids further down the line if gets worse.

 

[Migizi]

Although no service light, I ran diagnostics with Carly and found this...

Engine / Motor
Fault Code: 002C7E
Fault Explanation: :Lambda probe on the catalyst, trimming control

Does anyone know which one of these o2 probe/sensors is Carly referencing , I certainly don’t want to replace a good probe

 

[Migizi]

I fixed it!

Using INPA, I did a Valvtronic Adaptation reset

 

[wonkydonkey]

Winner! 8)

 

[firebobby]

:happyclap: :happyclap:
Who's a clever boy

 

[kis]

Out of interest was this anything to do with the fault code stored? (That you mentioned previously?)

 

[Migizi]

Out of interest was this anything to do with the fault code stored? (That you mentioned previously?)

not that I could tell

 

[ph001]

Can you run through how you get to this in INPA please? Sounds like a few cars might benefit from it as time goes on.

 

[Capa]

The above would be beneficial, for sure.

Also - I see a lot of people suggesting that you can remove the eccentric position sensor whilst the car is runninig.... If you do this to mine, it dies... Is this evidence of a fault with it?

 

[Flyingfifer]

Can you run through how you get to this in INPA please? Sounds like a few cars might benefit from it as time goes on.

+1 I had this issue and several others had the same

Damn good work Migizi!

 

[Migizi]

 

[Migizi]

Out of interest was this anything to do with the fault code stored? (That you mentioned previously?)

not that I could tell

After some more thought...yes, possibly.
Since I have completed the valvetronic adaptation reset, that lambda fault has not re-occurred

 

[Ewazix]

It's always satisfying to find a fix?

Just to clarify for anybody looking for answers to dodgy idle, this fix presumably only applies to N52 facelift cars with Valvtronic, not the pre-facelift M54 or S54?

 

[Migizi]

...Just to clarify for anybody looking for answers to dodgy idle, this fix presumably only applies to N52 facelift cars with Valvtronic, not the pre-facelift M54 or S54?

Correct, my engine is the N52 with Valvetronic.
I have updated the 1st post with that additional info.

 

[ph001]

Great instruction Migizi, thanks for posting. Tagged #valvetronic #adaptation #reset