extra air valve - not working?
extra air valve - not working?
Author
Discussion

sprevett

Original Poster:

534 posts

247 months

Thursday 15th February 2007
quotequote all
my 350i seems, when cold, to get spurts of power in a rather jerky kind of way until warm and then all is well. could it be the extra air thingy not working properly? how do they work?

l33

3,469 posts

253 months

Thursday 15th February 2007
quotequote all
If its the valve I'm thinking of, its an extra injector, its bugger all use in this country unless temp gets well below zero. Many of us have disconnected it.
If its any consilation, many of our wedgers are a little jerky until they have warmed up fully.

thumbup

Edited in lieu of Rev's comment

Edited by l33 on Thursday 15th February 11:38

sprevett

Original Poster:

534 posts

247 months

Thursday 15th February 2007
quotequote all
ah...nuff said. ta

rev-erend

21,619 posts

313 months

Thursday 15th February 2007
quotequote all
Have you disconnect the cold start 'extra' injector yet..

No one bothers with them anymore - they put pour in around a pint of petrol in the 1 min that that are working..

sprevett

Original Poster:

534 posts

247 months

Thursday 15th February 2007
quotequote all
is that the one in the top of the plenum?

rev-erend

21,619 posts

313 months

Thursday 15th February 2007
quotequote all
sprevett said:
is that the one in the top of the plenum?


Yes..

leorest

2,346 posts

268 months

Thursday 15th February 2007
quotequote all
This is how I remember the workings of the Extra Air Valve (EAV)...

The EAV is a disk which has a tapered slot in it. As the disc rotates the slot passes between the input and output ports allowing a variable restriction in the amount of extra air admitted. The rotation is controlled by a bimetallic spring and therefore it's position is temperature dependant.

Low temp = maximum extra air (large part of the slot is presented between the ports)
High temp = no extra air (the slot is moved passed the ports and they are blocked by a blank part of the disk)

The heating effect is primarily from thermal contact to the engine block but there is also an electric heater (controlled by the thermotime switch).

As this is a mechanical device with air passing through it, it is prone to getting gummed up and sticking. It can be easily removed from the car and washed out with solvent and finally given a spray with WD40 to lubricate it.

There is no mysterious monitoring and control by the ECU in fact it is not aware of it's existence.

I think that's reasonably accurate. Someone will no doubt correct any errors/omissions.

HTH
Leo

BTW the Cold Start Injector (CSI) is a separate device, just an additional injector on top of the plenum. Usually disconnected in the milder climates.


Edited by leorest on Thursday 15th February 18:32