update: no idle help

[Bernard Littau]

I finally figured out the no idle problem (several of you, thank you all!,
ask for updates with your advice...).  It was a IC to TB (Intercooler to
Throttle-Body) hose problem.

I have a single pass IC on my 5ktq, and I had pretty much, incorrectly,
ruled out the IC circuit as I had blown a hose previously near the turbo,
and the previous behavior of a blow hose in the IC circuit was way different
than what I was experiencing with the hose being loose on the TB.

Some of this was complicated by my having to replace the distributor.  I
indeed had a flaky Hall Sensor.  The alignment was correct, the old one was
just flaky.  At one point I started getting Hall Sensor codes, and although
some suggested this might be an alignment problem, it was indeed a bad Hall
Sensor. When I got the new distributor, I ran the old and new distributors
back to back on a 12V bench power supply into a oscilloscope, spinning the
shaft by hand.  There was a clear difference in the output of the new vs.
the old units.

I mush have blown the IC to TB hose at the same time as the worst of the
hall sensor mess was happening, so I didn't notice it per se.  (the Audi did
get me home, but it wasn't pretty, and I'm sure I had some WOT backfires on
the way home  :-)

With the new distributor (new Hall Sensor), the car ran great but would not
idle.  I was getting no codes, so I started checking stuff, led mainly by
Scott Mockery's web site.  The ISV was close to within his spec, and the
Decel valve seemed fine, and having decided it couldn't be a Turbo-IC-TB
problem because I "knew" that behavior, I called for help on the list.

I finally checked "everything" and found the IC to TB hose had blown off the
TB, but was being held mostly in place by the IC.  Live and learn.

One of the lessons I though I learned earlier, but apparently not well
enough, was that the hoses on boosted engines need to be more tight than I
normally make hoses.  I've wrenched cars for a long time, and have worked
out how tight I like to make coolant hoses to minimize the hose distortsion
and yet be tight enough to hold against the 15 or so psi max pressure in the
coolant system.  My attempt to apply this same technique to the air
induction system had failed several times now with hoses blowing off as I am
re-learning hose clamp tightening 101.  At 2.0 bar boost, with spikes above
that in spite of a recirculation valve, hoses clamps need to be damn tight.
Good thing I own a 6mm wrench :-)

Best,

Bernard Littau
Woodinville, WA
'88 5ktq