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

William Jahn willjahn975 at gmail.com
Thu Jun 6 15:09:34 PDT 2019

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 . 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. I was trying to figure out why when I have no load on the
engine it's in park and I bring it up from 1000 RPM to around 1500 it's a
smooth transition only if the engine is warmed up for 10 to 15 minutes and
the IAD temp sensor is unplugged. If I just start the engine cold then it
works fine with that sensor plugged in. Did you ever get a chance to see
what your 73 does with that sensor unplugged? Before i changed the runner
boots and vacuum lines it acted this way even cold so something changed. I
drove it today and I do feel a bit more pickup since I adjusted the TPS yet
nothing else changed. seems the only issue is the AAR not closing fully is
giving me the high idle or 1300 RPM once it runs for a few minutes only in
park , the odd part is when it's in drive the idle is 1000 if it place it
in park it does not just jump to 1300 it climbs from 1000 to 1300 takes
about 30 seconds. When it's at 1300 and placed in drive it's an instant
drop to 1000 RPM which seems to be the load the auto trans places on the
engine. Maybe the gradual rise is the time it takes for the MPS to adapt to
the vacuum change. I don't know. I never had these issues before it just
worked as it should so I never tried to figure out how it all works
together until 2009.

On Thu, Jun 6, 2019 at 2:20 PM Jim Adney <jadney at vwtype3.org> wrote:

> On 6 Jun 2019 at 10:46, William Jahn wrote:
> > I felt the idle contact was the most important , it's there for a
> > reason , don't know exactly what it's function is in relation to what
> > the ECU see's.
> It's function is to turn the FI off when you take your foot off the gas
> but the
> RPMs are still high, as in when you're coasting down to a stop light.
> During
> that time, the brain turns the FI off, so you don't use any fuel, get
> maximum
> gas mileage, and, ideally, pollute as little as possible.
> This works if the RPMs are above something like 1400 and continues until
> the RPMs drop to something like 1100.
> --
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
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