[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

Re: O2 sensors

In a message dated 97-11-11 14:57:01 EST, you write:

<< On turbos are there any real symptoms of a failing or failed o2 sensor?
 >Could my 1.3 bar bog be caused by it? I was under the impression that
 >maybe symptoms of a failing sensor are gradual and you don't really notice
> it until you change the sensor. Do higher boost levels affect it's life?
> Audis are built around the airbox? I say they're (at least turbos) built
> around the o2 sensor.
The bog is caused by something else, could be fuel related tho.  Remember,
the lamda circuit (O2) goes closed loop at WOT, in other words, it fixes a
value for the O2 circuit (voltage/Duty Cycle).  Not sure I understand the
latter part of the post, but a failing O2 can have the following
characteristics:  Intermittent FV operation at idle, poor idle, poor off
boost peformance, bad mileage (this one is my benchmark).  A DC or dwell
meter can be a good indicator as well.  As an O2 starts to fail, the variance
from it's read start to get wider.  IOW, put in a new O2, set to 42DC/37.5
dwell.  You will get a variance in that DC/Dwell of about +/-5 or less on a
new O2.  Older O2's will jump +/-10 or more as they fail.  

You certainly could have a fuel problem.  System Pressure and Control
Pressures should be tested periodically (change fuel filter first please),
you can save a lot of diagnostic time by making sure you have those correct
baseline.  An A/F meter might help you establish whether you are really
"lean" or "rich" and at what rpm.   Turbo cars with no fuel mods tend to run
a little rich at around 33-3800rpm (torque peak), especially with  boost
upgrades.  "Adj" in your tag line indicates that you have an adj WG spring
preload.  You might have that dialed down a tad too much for the fuel