Got a multi-meter with a duty cycle. Followed instructions, red in #3 black in #2 in the test socket on the 91 300e.

Turned on the ignition, but before starting 84% reading and even after the engine is running I still get 81%. The value does not fluctuate.

-Does this mean the oxygen sensor is bad? or .....

-Does this mean the air/fuel mixture adjustment is off the charts?

Haasman

__________________
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)

Did you let the car reach the normal operating temperature before you took the reading?
If it is taken on a normal operating temp. I believe you are running lean, your fuel consumption should be way off also. You should be able to adjust the mixture, as for Oxygen sensor is concern, this alone should not be the determinig factor. Do the test on the sensor itself, there is a procedure out there on these threads for that.

You might already have them but just in case Few good readings on duty cycle
'86 300E rich mixture - Duty cycle help

http://www.peachparts.com/Wikka/EngineControls

http://www.landiss.com/mixture.htm

Hope this is helpul.

__________________
87 420 SEL
Looking for a nice mid 80's MB diesel.
87 BMW 528e (Sold)
99 TOYOTA 4Runner
1989 Honda Accord (Sold)
1988 Honda Accord (Total)

Went out and got it warm and it still reads 81.3-81.7% on the duty cycle setting.

I tried turning the 3mm both clockwise and counter clockwise but didn't influence the read out at all.

Am I so out of range that I am getting this reading? If so which way should I turn the adjuster?

(Below is the meter I bought from Sears for $29.95)

Thanks,

Haasman

Attached Thumbnails

 

__________________
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)

To which car are you referring? Year/model make a difference for this.
I believe you have a California car (which is indicated by 85% duty cycle at X11 between terminal #3 [+] and terminal #2 [-] with: ignition on engine off)

From my reading of the CD (and I may have this wrong).
You will have to read faults at X92 terminal (near battery) with an LED pulse counter like Arthur Daltons: http://members.aol.com/ajdalton7/ledtool.jpg

It could be that: Only once a pulse reading is taken can you test duty cycle at X11?

But if your Duty cycle reading means something it might be this:
80%
Open circuit or short to ground.
Air intake temperature sensor (B17/2) faulty
Altitude correction sensor (B18) faulty
Test Air intake temperature sensor.
Test Altitude correction sensor.

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

Marty

Thanks, I edited my original post for which car (91 300e). Sorry about that.

Seems like a long list .... I will check the codes and report back after I make an "Arthur Daltons Special Tester".

The engine must be running too lean because it stumbles in throttle transition from idle to mid RPMs. At a sustained RPM seems fine.

Haasman

__________________
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)

Are you sure your meter is set for duty cycle (%) not for frequency (Hz)? Upper left button change between duty/frequency.

Roman

__________________
Roman
_____________
83 280SL 145K (5 spd)
_____________