re: O2 LIGHT IS ON

["A. D. Morris" <allanm@primenet.com>]

>From: dougev <dougev@newpig3.newpig.com>
>Date: Wed, 4 Sep 1996 08:55:09 -0400
>Subject: O2 LIGHT IS ON  
>
>This message is in MIME format. Since your mail reader does not
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Actually the digest does not understand MIME.

Doug, consider sending messages to the list without MIME...

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>Dear Quattro Owners. 
> My wife has informed me that the "little light with the lightening
>bolt going through it" is coming on in her 1988 90Q. 

"coming on"?  This means one thing, staying on means something else.  
If it stays on, it has a fault stored in memory, if it flashes. . .

> Translation....The Oxygen Sensor Light .  When this light comes on

Translation, Check Engine Light.

>does it mean the O2 sensor must be changed?  

Nope.  The sensor should probably be changed at 60,000 miles, 
although YMMV.

>Or does it come on at "X"
>number of miles regardless of the sensor performance?   

Nope.  It will come on if the sensor totally dies, but probably not 
until the sensor is in very bad shape.

>If it has to
>be changed, is it an easy thing to do?   

Yes, it is on the Catalytic Converter, and can be removed with an 
Open ended wrench.  

>And how do you reset the
>light? 

You don't, it's on for other reasons.

>  Any and all help would be appreciated.
>Thank you in advance,
>
>Doug Evens
>dougev@newpig.com
>85   4000S QUATTRO
>88   90 QUATTRO
>84   325e
>

Possible reasons check engine light comes on intermittently:
1)  Knock sensor is causing max retard on timing (15 degrees, I 
think).  This is caused by bad (cheap) gas.  Try a different brand/or 
station.  And only use Premium (92 octane ?)

2)  Other intermittent out of range input to ECUs (Yes, 2 of them). - 
Such as intermittent O2 signal, etc....With a Bentley, which are out 
of print for this car (they are supposed to be printing another 
batch), you can list the fault codes stored for the car, which 
*should* tell you the faulty piece(s).  If you are interested in the 
procedures for reading this, drop me a line, & I'll e-mail the 
procedure- they are fairly easy.

3)  I think there is a problem with the CIS-III (88-91 NG and NF
engines)  ECUs which causes this problem (Others here disagree, but
we are all entitled to our own opinions :)  And no, I don't have a
solution :( 
-----------------------------------
A. D. Morris
Phoenix, AZ
allanm@primenet.com
-----------------------------------