AAV throttle stop screw

[zob 27]

 

 

I was cleaning up the throttle body ahead of the MOT and noticed that the stop screw for the throttle cable pull (pictured) never actually comes in contact with the plate that meets it. I assume its there to act as an adjustment for where the throttle would stop - wouldn't this count as an idle throttle adjustment? The engine rattles along at 800rpm at idle so I assume nothing is out of the ordinary here, but what is it actually supposed to be for?

 

 

 

 

[steveo3002 522]

pretty sure it should be that that it stops against 

[zob 27]

Aye me too. Perhaps to take the spring load off the butterfly? Just to be clear, even with the throttle cable removed this gap between the plate and screw remains so its not from the cable pulling it away.

 

Has anyone seen any advice on setting up this screw? I can't find anything in the usual places (doesn't even seem to be on 7zap), plus the screw head is round, nothing to get purchase on to turn it.

[zob 27]

From an old thread:

So i guess its there as a fine-tune for idle speed. Might have a fiddle with it to see what difference it makes

 

[steveo3002 522]

think it will ecu controling the idle...id just wind it in until it touches

[zob 27]

Seeing as there's nothing actually wrong with my idle (that i know of!) i think I'll do just that. Its interesting though - its obviously designed to be adjustable but the SPI throttle body is not supposed to be.

 

The ECU sets the idle through the injector fueling schedule based on the throttle butterfly position - so manually setting this throttle stop any further than just touching should technically set the idle, albeit only higher than 800rpm. I guess what interests me is why anyone would want/need to do that? Perhaps it was for some initial set-up that VW would do in the factory?

[steveo3002 522]

id imagine its factory set , if its not resting on that then its putting strain on the butterfly ?

 

i have info for other cars basically says dont touch it but if you do move it so it just contacts 

[zob 27]

I would have thought the butterfly is taking all the force from that spring tension yeah. I'll wind it in till it contacts, but maybe a remove/clean/threadlock might be a good idea too seeing as it may have vibrated loose over time.

 

 

[zob 27]

Well I had a look at it just now and short of cutting a slot in it'd head or bashing it with a punch I can't see how you're supposed to move that thing (probably why it was factory set, eh?). The round head also sits in a semi-open tube so you can only touch one side of it as well - no way to get grip on it. Its evidently not designed to be messed with and I could see no signs of anyone mucking with it in the past - I just put some marks on it with some very light tampering so my money is on it being like that for a very long time, probably even forever.