[T3] Since I replaced the runner boots and all vacuum lines noticed

Jim Adney jadney at vwtype3.org
Fri Jun 7 08:18:12 PDT 2019

On 6 Jun 2019 at 15:09, William Jahn wrote:

> Does this mean @ idle all that tells the ECU to fire the injectors are the
> trigger points?


> I am trying to figure out how this works since my idle
> because of the AAR is 1300 RPM in park and 1000 in drive. 

There's really no mystery as to why the rpms are lower under load than 
without load.

> I thought once
> you let off the gas due to the 2 way switch once you let off the gas then
> that switch cuts off all the functions of the enrichment didn't know it was
> RPM dependent.

The @ idle switch has nothing to do with enrichment. In the idle position, the 
enrichment contacts are not in use.

> Did you ever get a chance to see
> what your 73 does with that sensor unplugged?

No, sorry, too many other things on my plate for that to rise to the top.

> Maybe the gradual rise is the time it takes for the MPS to adapt to
> the vacuum change.

There's a spring loaded flapper valve in the MPS inlet that alters the MPS 
response time depending on whether air is trying to get in or get out. The 
delay on opening the throttle is less than on closing. I'm guessing they are 
on the order of 0.5 sec and 3 sec. I don't think there's any measurable 
response time in addition to that.

Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA

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