Late Model CIS-E Diagnostic / Duty Cyle Help

[JamesDean]

CAR: 1993 190E with 3.0L from 90' 300SEL (85k miles)


For the past several months I've been trying to diagnose/fix my air fuel mixture. I'll be as detailed as I possibly can. As I understand it from multiple sources I can read duty cycle from X11/3 port. If I want diag codes I have to do some other things and they will be output for me via that same port. I havent done this yet as I'm not sure about the procedure. I'll post what I've done so far. Hopefully someone can spot something...I'll post this across a few MB boards I'm on in case some people arent members there etc etc.

Heres the story:

In March, I just had a 3L m103 put in. It was running around 20%-25% Duty Cycle. I started the procedure to adjust it to the proper 50%. A friend of mine walked me though it. I increased the EHA about 1/6 turn. It brought the mixture to around 40-45%. Then I went to adjust the Lambda tower to fine tune it. I mistakenly did so with the car off (after the adjustment I stared the car, waited for the mechanical control to give way to electronics and observed the duty cycle) I did this twice. My final reading was still around 40-45%. As I was waiting for the mechanical control to switch over to electronic I decided it would be a good idea to clean my passenger seat area. Now whether this was coincidence or not, The duty cycle signal dropped off. It climbed up towards 100% and on the scope I had at the time went to 0v. My voltmeter tells me .09v.

And thats where I am right now.

I swapped EHAs with my old 2.6 motor thinking maybe it would do somthing (anything really to effect the voltage there) but it did nothing.

Then HefDMC over here clued me into the fact that, the 99% could mean something in the FSM. Sure enough I looked it up and the FSM said:



I've checked:
Lambda Control. Everytime I adjust it. The DC will
appear then slowly fade down back to 100%.

Oxygen Sensor was just replaced and has no shorts that I can detect

Control Unit [CIS-E] was swapped into my buddy's 300SE and ran fine. His was swapped into my car and showed the same results.

EHA: has continuity between CIS-E and plug ends. Draws current fine. It considered to be working.

And they listed a procedure lower in the PDF on what to test if you have a 100% (non oscillating) DC: I'll lead you down the path I've taken.

It begins:

1) Test Adjustment of Lambda Control.
"On-off ratio can be regulated. Read Out Oscillating" OK / NOT OK.

2) NOT OK:
Disconnect 02 sensor signal. Check Voltage from CIS-E to ground: 450-1000mV.

3) OK:
Test Line to CIS-E control unit jack 8 for continuity.
Resistance approx 0 Ohms. Here is the diagram they provided for this:



Now, here is where it starts to fall apart. 1) my CIS-E doesnt have the same amount of connectors as this diagram. 2) I get no continuity at all between the CIS-E and o2 signal. However, I get the same result from a 90 300SE who is in working order and has good afm/dc

4) The last test in this category is the voltage to the heater lines of the o2. Mine Tested fine.

So this is where I am right now. I really dont know what else to do. I dont want to take it to the dealer and get reamed out the ass with high bills and what not.