Job 07.3-121 Help
 

I'm running out of ideas at this point. I've started several threads on a driveability issue with a '90 300E, and am not getting any input to speak of.
This is a continuation of the Huge Flat Spot / O2 Sensor wiring threads.
I got a chance to check out the O2 Sensor-to-Control Unit wire, and it checks out at 0 Ohms, and is not shorted to the shield, but the shield shows about 4 K Ohms to ground (Pin 32, if I recall correctly).
The O2 Sensor is putting out about 0.9 VDC at idle when warmed up, and 12-15 mV at 2K rpms.
Idle Duty Cycle cold is 50%
Idle Duty Cycle hot is locked in at 8-10%, i.e dead rich.
Duty Cycle is unresponsive to connecting/disconnecting the O2 Sensor.
Air Flow pot was cleaned and adjusted to a minimum Pin 2 reading of 0.9 VDC, it would not go down to 0.6-0.7 VDC.
Could anyone help me out with this test routine for the Air Flow Pot, Job 07.3-121. I don't have access to any printed or virtual information yet.
Also looking for a recommendation for book, or CD compatable with Win 95/98 that could help.
Plugs, wires and cap have already been replaced.
Car is currently running semi OK with EHA disconnected, and dead rich with EHA connected, w/huge midrange flat spot.
Help.
Mark

this is a good thread:
http://www.peachparts.com/shopforum/tech-help/62226-help-please.html?highlight=duty+cycles

and...
http://www.peachparts.com/shopforum/tech-help/61858-setting-new-airflow-meter-190-16v.html

these don't refer to your symptoms but give an overall assessment of the lambda and ignitions systems. As a tip that I would pass on, the MB manual states to always inspect/troubleshoot the EZL before the CIS

By those figures you have a RICH mixture! Have you tried leaning out the adjustment until the engine stalls out?? or the duty cycle heads to the lean side? ON that car the coolant temp & air flow sensor suggest the largest fuel mixture corrections to the ECU

Many thanks
 

Thanks guys,
Looking at the resistance specs for a new unit, I can clearly see that mine is hosed. I'll replace it and get back to you.
Here are my specs, as last measured:

Between Top and Center Pin
closed 20K
1-2mm 3-4K
.25" 5K
.5" 7K
1" 9K
1.5" 10K
2" 9K
WOT 8K
Between Center and Bottom Pins
Closed 20K
1-2mm 10K
.25" 10K
.5" 6K
1.0" 7K
1.5" 7K
2.0" 6K
WOT 6K
Here are the specs of a new Pot, based on UKEvos measurements.
35mm 1.070k (First place I see a change)
35.80mm 2.00k (Very rapid ramp up to 2.0K from 1K in the space of less than a single mm)

36mm 2.35k
37mm 3.35k
38mm 4.25k
39mm 4.95k
40mm 5.55k
41mm 5.95k
42mm 6.35k
43mm 6.80k
44mm 7.10k
45mm 7.30k
46mm 7.60k
47mm 7.80k
48mm 7.90k
49mm 8.15k
50mm 8.20k
51mm 8.20k
52mm 8.28k
53mm 8.28k
54mm 8.32k
55mm 8.50k
60mm 9.40k

65mm 9.50k (peaks here, then begins to fall)

68mm 9.40k
70mm 9.20k
71mm 9.10k
72mm 8.90k
73mm 8.80k
74mm 8.60k
75mm 8.45k
76mm 8.25k
77mm 8.10k
78mm 7.85k
79mm 7.60k

80mm 7.50k (Plate bottoms out - no more travel).
I don't think he mentions which pins he's measuring against, but its clear that mine is toast.
Thanks all.. and let that be a cautionary tale to everyone else with these symptoms...

It is possible to replace just the potentiometer and not the entire airflow meter. I believe the pot alone is around $180

I have found references to the pot being available for under $100.
Will let you know.