Duty cycle/EHA current , 2 pictures from meters
 

Top meter is EHA current and red meter is duty cycle. Duty cycle was jumping between 78 and 94%.

This is with the o2 sensor unplugged. Any one know what this means?

Your camera needs new batteries because it's taking too long for the flash to charge? Just kidding :)

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

What car? Is this at idle, and if so, was the idle speed steady and what was the rpm?

Steve

well the eha is reading a rich reading while the other is reading lean what i did was adjust the mixture screw to maiting a little rich reading at idle and at 2000rpm the other meter to read no more than65% you will notice taking impresive throttle respond no more lagging taking off

89 3ooe M103 @ 2000 RPM (same readings at idle). I adjusted the mixture screw until it killed the engine, but it didn't change the readings.

i re read the post you said 02 disconnected if so then it should of went to 50% and eha to lean

I want one of those multimeter units,but I do not have the slightest idea how to use one. Are they that complicated to use??

I can't read the second picture, but if the O2 sensor is disconnected the eHA should go to 0.0ma and the duty-cycle to 50%.

The first picture denotes a rich mixture from the EHA current of minus 3ma. The duty-cycle is backwards or the polarity is backwards. A 68%duty-cycle would indicate a lean mixture.

The first picture denotes a rich mixture from the EHA current of minus 3ma. The duty-cycle is backwards or the polarity is backwards. A 68%duty-cycle would indicate a lean mixture.

steve is this normal my car shows. it that way too
rich reading at eha and lean on dutycycle

Duty cycle represents a point of view. Sixty-eight percent on duty cycle is the same as 32% off duty-cycle. Most meters have switches that invert the readings. If the EHA is right (the way to tell this is the key on engine off current. it will always be positive) then the duty cycle should be reversed for convention.

I turned the camera flash off for the second picture, should've left it on! The meter readings for the second picture are almost identical to the first. So, no change when o2 sensor was unplugged. As I said, the duty cycle bounced from 94 to 78, actually spending more time at 94%. So, if it's that lean where's the gas going? 12 miles per gallon. Cold start injector is plugged off. EHA (or anthing else for that matter) is not leaking externally.

Cap'n,
are you sure that you disconnected the 02 sensor?
You might have disconnected the heater wire or some other thing but not the 02 sensor.

I disconnected both the heater and the sensor.

All that matters is the EHA current. The duty-cycle is only an easy way to see a similar representation of closed loop control.

Could anyone recommend a harness for measuring eha current? Where can I find one? Bosch?!

Look at 3rd post by PMIZELL in this thread. Contains MB part number:

http://www.peachparts.com/shopforum/showthread.php?threadid=47986&highlight=harness

Cap'n,
The multimeter you have is the same as mine and steve is right it measures duty cycle backwards. the red connector in 2 and black in 3 should give you the right numbers. I would expect your duty cycle to be around 20 to 30 this way. Depending on your car and X11 jack 'key on engine off' should give you 70%, if you get thirty either your coolant temp sensor is dead or your poles are switched. The chances of the coolant temp sensor being bad are negligible. So switch the poles then use that as your duty cycle. I based this on my car a 91 560sel. The manual should give you this info and I think it is fairly similar for most benz's. 190's I believe will give a different EHA reading though.