BMW error code and cold start roughness

[danlightbulb]

Hi all

Will be selling the car in a few weeks time when I get my new one.

For some time it's been having a rough start up, as if it's misfiring. It happens when it's been sitting for a few hours. For about 10 seconds, it is lumpy, sounds like it's misfiring. Then it settles down and smooths out, and after that drives fine.

It's also started using some coolant. Can't see a leak.

Finally got around to reading the error codes today and there is one code that won't go away. Error code 2aa9 which is called "variable intake system positioning motor 2 activation".

A bit of googling suggests this is a DISA valve 2 failure, which is located under the intake manifold.

I'm not sure what this part does, but would it cause a misfiring/lumpy idle like symptom on a cold start?

I don't think it would be related to slight coolant loss. Do you think a bit of radweld would be worth trying on the coolant loss side?

 

[Scania]

If the DISA valve fails completely, your engine may end up sucking parts from the failed valve into your cylinder head, which can destroy your engine.

From what I've read it can cause a rough idle as a symptom.

Can you hear any rattling coming from the manifold?

 

[radderfire]

What model is it?

 

[SkodaMart]

Disa is a device (flap) in the intake manifold to vary the distance the intake air has to travel to create either high torque at low rpm or high power at high rpm.

I replaced both of mine on my N52B30

 

[danlightbulb]

What model is it?

325i, n52 engine.

Disa is a device (flap) in the intake manifold to vary the distance the intake air has to travel to create either high torque at low rpm or high power at high rpm.

I replaced both of mine on my N52B30

Yeah strange isn't it, how adding resistance to the intake air can increase torque. I wish manufacturers would just keep things simple and not have these superfluous bits and bobs all over the place.


Just contemplating whether I need to do the job or sell the car with known fault.

 

[SkodaMart]

325i, n52 engine.



Yeah strange isn't it, how adding resistance to the intake air can increase torque. I wish manufacturers would just keep things simple and not have these superfluous bits and bobs all over the place.


Just contemplating whether I need to do the job or sell the car with known fault.

The N52 is a marvellous piece of engineering - I’m now on my second one.
You can’t have linear power, economy, low down torque without these gadgets in a normally aspirated engine sadly.
It is both a low power high torque engine and a high lift peaky cam engine in one and it does this seamlessly.
As you can probably tell I’m a big fan of the N52.
A turbo achieves all this in a far more crude albeit simpler way, but those come with problems too.
If you had told me 20 years ago that a 3 litre normally aspirated BMW engine could return better cruising MPG than my 1.8 20VT (42 vs 38)
I would have said it was nonsense.