[W126 Coupe] Rear End Thumpety-Thump & O2 Sensor Readings

[Alexander Hochhausl]

Good Info. The last paragraph of the 3rd reference has the numbers I was
looking for. I have the Bosch manual which goes into all the other info.
My issue is during the times the motor runs "open loop" (start, warm-up)
and when I override the mixture control (during boost) the motors runs
normal. During highway cruising though I see I am at ~ 16 in HG vs
18-19, so I think I am running lean, requiring a bit more throttle.
That's my theory anyway - to be proven (or not) this week-end.
 
Thanks for the help.
 
Alexander Hochhausl, PE
Tel: 516-909-3794
 
-----Original Message-----
From: mbcoupes-bounces at mbcoupes.com
[mailto:mbcoupes-bounces at mbcoupes.com] On Behalf Of Dan Landiss
Sent: Monday, March 03, 2008 7:41 PM
To: Mercedes Coupes Mailing Lists
Subject: Re: [W126 Coupe] Rear End Thumpety-Thump & O2 Sensor Readings
 
on 3/3/2008 6:17 PM Alexander Hochhausl wrote: 
Second - does anyone know what the "normal" voltage reading for the O2
sensor should be? I can't find it in the service manual I have.

Measuring the O2 sensor voltage directly is not a normal service
procedure. The system is set up so that it hunts back-and-forth around
the stoichiometric air:fuel ratio. The duty cycle of that hunting,
rather than the actual sensor voltage, is most often measured.

Here are some curves:
 
<http://www.pelicanparts.com/techarticles/mult_air_fuel_monitor/mult_air
_fuel_monitor.htm>
<http://www.pelicanparts.com/techarticles/mult_air_fuel_monitor/mult_air
_fuel_monitor.htm>

Although written for a Volvo site, this is a pretty good description of
how it works:
 <http://www.volvoclub.org.uk/tech/fuel_injection/k_jetronic.shtml>
<http://www.volvoclub.org.uk/tech/fuel_injection/k_jetronic.shtml>

And a procedure for adjusting it:
 <http://landiss.com/mixture.htm> <http://landiss.com/mixture.htm>



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