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?

 

[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.