Duty cycle/EHA tests.....Round two
 

I reversed the leads on the duty cycle tester. Key on ignition off gave zero numbers for both meters. On ignition I got this;

Then this at 2000 rpm

Then this at return to idle. ?????

Then this...

Fianally this...

And a picture of part of the soot on the floor from the exhaust.

Adjusting the mixture screw had no effect on any meter readings, it just made the engine run worse.

Sorry to complain, but it is still rather difficult to read from some of your pics - is that a vacuum gauge, tach?. In many cases, such as id on a part, or showing how something is assembled, etc, a pic really can be worth a thousand words. In this case, though, a few dozen would be lots better. All the meters are telling you is data, and tabulating it in text is far the easiest way to read it.

Now it is possible the equipment is hooked up wrong, and someone might spot that in a flawless pic, if true. That, though, might require the resources of a good photography studio. This automotive stuff often seems to be highly non-photogenic.

Anyway, IMHO. Don't want to offend, just to help you get your problem resolved. My meager input on your problem is that if mixture adjustment does not affect EHA current, you are open loop - no lambda control. Does your OVP work?

Steve

when i had that same problem it turn out my fuel distributor went bad.the part i keep asking and never get an answer
why when the eha reads rich the dutycycle reads lean just like in your pictures.then when the eha reads lean the dutycycles read
rich
steve said worried about the eha reading but all the info refers
to x11 for all diagnostic if you modified you air intake to bring in more air then you need to richen the fuel a little to match the air coming in. more air than fuel choke the engine and vise versa
also why is it everyybody discribe the same exsact problem
but the fix is different .

The guage is fuel pressure at the cold start valve port. It was steady at 5.5 bar falling to 3.5 bar with the engine off. The basics of the meter readings were a constant 39.3% on lambda except when it jumps to 96% and then returns to 39.3.% The eha readings are very active though. I tried to focus more on them than the lambda. OVP 'appears' to be working, I have power to the ABS and idle controller. Although the vacuum guage is not in the pictures, it read a steady 7.5 inHg. In addition, grounding the controller side of the O2 sensor through my body made no change to the EHA current. It's almost as if this thing is in 'partial' open loop. I have read that a fixed lambda reading in multiples of 10 indicates a fault, although I don't know what that would be for 40%.

capn,
I had the same problem with my readings except my eha was static as well. I am assuming you are using the eha cable that mb makes for diagnostics. The sears multimeter the positive(red) should be on the #2 port and negative (black) should be on the #3 port of the x11. Key on engine off should read 70%, if not then chack the cd manual it will tell you the error. If this is not fluctuating then you are in an open loop. The EHA as steve says is the key to adjust the system to your eha number and the duty cycle should match, although the O2 sensor should effect the eha reading.
good luck.
m

Key on engine off should read 70%, if not then chack the cd manual it will tell you the error
it suppose to read 50% not 70%

Josev,
You may be right I am talking about a 560sel and it should read 70% or 80% if it is a california car. So Capn check the manual for your car it should tell you the correct setting for your year and model.

Re: Duty cycle/EHA tests.....Round two
 

Oops, that statement is incorrect, Key on, engine off reading was 69.3% on duty cycle and +20.00 ma on EHA.

looks good thats what you should get.
m

OK, so key on engine off is where it should be, the the problem starts on ignition. Anyone have a clue what fault a fixed 40% and fixed 96% duty cycle indicates?

I have forgotten what car we are taking about?

89 M103

fixed 40 % says open circuit or short circuit to air flow sensor potentiometer or faulty. Possibly,fast idling speed. Test air flow sensor potentiometer. Test wiring, cis-e control unit.
96 usually points to an open circuit some where. Bear in mind this is my 560 manual.
m

woops next page 100 says: Lambda setting too lean. O2 sensor faulty short to ground. No voltage or ground at cis-e control or cis-e control unit faulty. lambda tester faulty.

things to do test overvoltage protection, test ground,test setting of lambda control and O2sensor signal cis-e faulty.

capn, I have found that the 96-97 reading was caused by my 4mm allen being over adjusted. and so my readings where all screwed up.
m

Mine only goes to 96% after it has been running for around 10 minutes. Then all of a sudden it will go back to 39.3%. Then it may go back to 96% and so on.

capn, thats what mine was doing. I also got this when i lost the eha current. But after adjusting the fuel mixture allen the problem went away and I get nice eha and duty cycle numbers. Still have the stall on acceleration but the electronics work.

m

The 100% reading (96) indicates the car is too lean. The fixed reading is either a result of that or the airflow pot as described.

While the reading is 40% there isn't much you can adjust, but when it is 100% try pushing down on the airflow meter flap. This should richen the mixture and if the O2 sensor is functioning the duty cycle should drop before you push so hard it starts running bad.

You should also disconnect the O2 sensor while reading 100%, it should immediately drop to 50%. I think the O2 sensor code 50% is the prevaling code. So it might even go to 50% when it is 40% if you disconnect.

Your explanation of grounding the O2 through your body is wrong! The test goes like this: simulate lean by grounding the sensor the duty cycle should head high. Simulate a rich mixture, run battery voltage through your body to the computor lead from the sensor: the duty cycle should go low. Running the O2 sensor input to ground through your body probably won't do anything.

The EHA current should go to +12ma when shorting the O2 input to ground and the current should go -12ma when the term sees battery voltage through ones body. (DO NOT HOOK battery voltage straight to the sensor input - we are trying to simulate 1-2v)

I have changed the sign convention twice now after rereading this. I think I got it right.

I would suspect either you are way off on mixture, or the O2 sensor is bad. One way or another, you aren't in closed loop mode (see steve's other posts, too!).

Don't adjust much at a time on the fuel distributor, and wait a while between adjustments -- I had the TE in almost the same state because I was expecting it to react too quickly. Takes 10 sec or so for the O2 sensor to register mixture changes at idle! Also, the pressure on the adjuster screws things up, I had to release the spring for it to stablize.

Mine is now at 50% duty cycle with constant variation, although I still have some intermittant miss vibration. Someday will take it down and stick the CO meter in the tailpipe and see if the mixture is out of synch with the controller. In the mean time, I'm running some injector cleaner in it and thinking of injector seals.

Peter