Running pig rich?

[Brady Moffatt]

I thought the O2 sensor worked at idle.

It's easy enough to check what O2 voltage the sensor is showing. Just
measure voltage between the single O2 connector and ground while the engine
is running and warmed up, and the O2 sensor is still connected.

Have you done the basics like plugs(OK, you did those), wires, cap, rotor,
vacuum leaks, timing, and DPR current (aim for approx 10mA)? Just changing
all the vacuum hoses I could see, and adjusting the DPR current back to 10mA
yielded a 15% improvement in fuel economy and much better power.

For the DPR current, you need to measure in series. See Huw's site for a
diagram of how to make an adapter.
http://www.humanspeakers.com/audi/timing2.htm#harness

Another thing to consider is the AC switch that wreaks havoc with the idle,
etc.

Cheers, Brady
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-----Original Message-----
From: quattro-bounces at audifans.com
[mailto:quattro-bounces at audifans.com]On Behalf Of Matt Suffern

Hi all,

Got the new fuel tank in my '86 4kq last Saturday and the car runs great.
Starts up every time without hesitation, pulls strong, doesn't cut out in
corners, steady cruising is a breeze.

The only problem is the car runs rich.  Really rich.  At any given time
there's a fine black mist emanating from the tailpipe, more so when the car
warms up.  At idle a nice haze forms behind me from the unburned fuel mist,
and sometimes (not always) at 80% throttle to WOT I can see a cloud pouring
out the tailpipe as I accelerate.  Also, as the car warms it will
progressively idle lower and lower until it will die unless I jab the gas
pedal.

I've replaced the plugs recently and also the coolant temp sensor (the one
at the bottom of the coolant neck leading from the head to the radiator).
If anything, the coolant temp sensor replacement made the problem worse, as
before it would occasionally idle (albeit high, around ~1200 rpm) when warm.
<snip>

Matt
'86 4kq
Chapel Hill, NC