cold start problems

Ti Kan ti at
Wed Jun 4 23:53:53 EDT 2003

Benjamin Weste Pearre writes:
> > How do you measure the CO mixture ?
> I must admit that I let a pro do that.  Diagnosing from scratch and
> fixing it took him about 30 minutes, not sure how long just making the
> adjustment would take.

To properly measure CO, one would need a exhaust CO meter, which is
probably not something that a typical home mechanic would have.  Basic
adjustment of CO on CIS cars is by inserting a long hex key into the the
adjustment hole in the fuel distributor and turning until the desired
CO level is achieved.  The oxygen sensor is disconnected when this
adjustment takes place to make the system run open loop.

For the home mechanic, one can get reasonably good results by measuring
the output voltage of the O2 sensor while making the adjustment (again,
the O2 sensor has to be disconnected).  A good voltmeter meter with
high input impedance should be used for this, so that the meter itself
does not load down the O2 sensor output and affect the reading.
A target of about 0.8V to 1V is usually good.  Then, when the O2 sensor
is reconnected, the closed loop feedback system will dynamically optimize
the actual mixture.

Since idle speed, ignition timing and CO are each related to each
other (vary one thing and the others change too), these three things
are often adjusted together.  In the case of ignition timing, some
models are are under tight control of the ECU and is not adjustable.
The idle speed adjustment procedure also varies from model to model,
depending on what type of idle stabilization system is equipped, etc.

2003 A4 1.8T multitronic
2001 S4 biturbo 6-sp
1984 5000S turbo
1980 4000 2.0 5-sp
    ///  Ti Kan                Vorsprung durch Technik
   ///   AMB Laboratories, Sunnyvale, CA. USA
  ///    ti at

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