CIS-E fun, facts, foibles, follies and fuestions

[doubt at inwave.com (Nate Mellom)]

A little history.
I bought my '88 16v in October 2005 from some poor soul who dumped $1500 
  at a local import shop to get his car running correctly (I have 
receipts).  New distributor, timing belt, fuel distributor work, etc, 
etc, etc.  He sold it to me for the princely sum of $800.  The issue? 
Stumbling, stuttering and a complete lack of power during acceleration. 
  It was barely drivable.  It got worse as the humidity went up.  I 
played and tinkered with it for months, new O2 sensor, made up a nifty 
DPR test rig, checked timing, but nothing.  When I checked my mixture, 
I'd get either 0.00 or 9.99mA.  I never got an honest number. 
Eventually I adjusted something (still not sure what worked), and it 
actually ran well enough to take on DD status.  I knew it was running 
WAY rich, I was using fuel like mad, and it stunk, and sometimes it was 
a little smoky.  A few months ago I swapped in a new cap and rotor, and 
the humidity-related stalling and stuttering cleared up.

Last week, I had it in for my favorite VW/Audi gurus to do wheel 
bearings, and for shits, I asked him to check my mixture (I still hadn't 
gotten a real reading).  When I picked it up, he was floored, even HE 
only got 9.99mA.  He told me he could play with it, do a pin test (per 
Bentley), he figured there was a broken wire somewhere, SOMETHING to 
explain the high reading.  He did play with the mixture, and was going 
to fiddle with it more, but I had to take it home.  It was like day 1 
again.  Stumbling, hesitation, hunting idle, and it would usually drop 
low enough to stall at a stop.  Got it home, played with mixture and 
idle settings until I thought it I got it right, took it to work the 
next day, same thing, a little better at best.  Got home, broke out the 
Bentley, found the CIS-E electrical test section, and went bananas.  I 
tested everything I could with one person (a few tests required cranking 
and testing), and found what I thought was a bad reading for the coolant 
temperature sensor reading.  Should be (x ohms @ x *c).  It didn't seem 
right for the temperature of the engine.  I pulled the wire off the 
sensor, sanded the connector all nice and shiny, plugged it back in 
and... Shit! A real reading!  And, it even matched what it should be, 
based on the chart!  Well, now we're cooking with gas!  So, I get back 
to checking for the magical 5mA.  Sure enough, 5 or 6 turns clockwise, I 
actually got a reading, then a range!  Dialed in 5, got my idle smooth 
and consistent, and whaduhyaknow?  The thing runs like a freaking top.

Lesson learned?  Check over everything, twice or thrice if need be, 
eliminate possible issues, and you'll have a good chance of finding the 
problems.

Now, some questions.

Someone posted on a VW forum a very good write-up on checking mixture 
and idle, and it helped me greatly.  At the end, he wrote to enhance 
performance in mid-range RPM power (4000 on up), to richen the mixture 
to about 2.5mA.  Is it a good idea?  Will I see results?  With the 
proper mixture it seems a little soft now, it seemed to have more zip 
when it was ear-tuned, so maybe?

My exhaust note seems louder now, since things are right.  Could this be 
because of the proper settings, or is my exhaust just failing, and 
they're just happening at the same time?

Sorry for the novel, my longest post in a long time.

Nate