hello steve
today i barrow my friends fluke meter to try and fix my problem
that i previously posted.steve at idle my eha reading is 9.89
when i try to bring it down to 7or 8 the car starts running real bad with a miss the duty cycle is from 2.6 to 3.4 more on the 3.0 side at times but before i made adjustments the duty cycle
was very irratic and at times no reading. but right now it's 3.0to 3.4engine sounds like is purring except for the eha high reading at idles.any idea as to what to check next to bring it down to specs .thanks jose

Your readings don't make sense to me. You mention duty cycle readings of 2.6, 3.4 and 3.0. Where are you reading these.

The EHA is measured with current and it will be 8ma at idle with the O2 sensor disconnected if we are talking an early 190 (like before 1986). All other KE cars should be a zero ma at idle with the O2 sensor disconnected. The others also can be tested by checking at key on engine off. They will read 20ma in that condition (in most cases).

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

steve i didn't disconnect the o2 sensor
also the duty cycle reading came from pin 3 of the plug that is on the driver side the one you unscrew the cap off.

Duty-cycles of 2.6 or 3.4 don't mean anything. I would interpret those readings as zero on pin three.

You need a reference. I still don't remember what car we are talking about but you should have 70% duty cycle on most vehicles with the key on and engine off. Duty cycle readings of a fixed amount that is a multiple of 10 are codes and an active reading gives a function of control (relative mixture).

All cars should have a reading of 50% with the O2 sensor disconnected. Get your readings gauged to one of these constants before deciding what you have in active mode.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

ok tommorrow i'll play with it again
the car is a 92 190e 2.6

steve i check the duty cycle on pin 3 of the 9 pin connector
call x11 with the car running i disconnected the o2sensor
the meter stood at 50.0 took a reading of the o2 while connected
.876 when i give it gas it drops down then it starts going up to .876 did the test you wrote just the wire going to the o2 sensor .889 rev the gas for 1minute the range never change
to cold outside test more tommorrow
thanks jose

You got 50% this is what I understand. What is itr after hooking up the sensor? Does it go to zero percent (or close)?

If the value .876 is voltage at the O2 sensor lead, then you are rich. Hold the engine at 2000rpms and adjust the screw till the voltage drops. It will go from where its at to near zero in only a few degrees rotation of the adjustment from where it starts to change the voltage. You must remember that the O2 sensor is only good for telling actual mixture in the range 0-1.0% CO (tailpipe tested). You will run great all the way to about 7% CO so you could have to adjust considerable before you hit the appropriate range.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

ok steve here is the latest.
meter connected to o2 sensor while driving varies
at idle 8.89. connected meter to eha valve=9.87
then when i disconnect the o2 sensor it drops to 2.35to3.45
ok now connected everything back to normal sampling the o2 sensor like you said at 2000rpm i adjusted the mixture screw
to 5.67to 6.98 and at idle it goes back to 8.89 but know the car idles like **** with a miss to it and hesitate while trying to rev up motor. if i bring it more toward the rich side the miss goes away idle is good and barely any hesitation any suggestion as what to next.thanks jose

Your numbers don't make any sense. O2 sensor voltages can't be 8. something. You need to give me numbers with units after; such as 0.727v or 20ma. You need to verify your readings with a standard.

If you wish to look at the EHA control it is done at the eHA and will be in ma and key on engine off should equal 20ma. See if this happens. O2 sensor voltage should never be anything but 0 to 1v. If you read the lead to the computer it should read .45v when disconnected from the sensor.

If you have O2 sensor voltage above 1v then the heater circuit is bleeding voltage through. It runs at battery voltage so in theory anything up to that could be transfered.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

STEVE i meant 0.889v and yes with the key on engine off eha valve is =19.99ma
and yes the wire from o2 to computer is 0.45v when disconnected

steve all the test fall into the correct reading.
today i check the airflow sensor specs from factory =3.6to4.4kohms.mine reads 1.36kohms so i assume this unit is bad and causing me the problems i need you imput on this
thanks jose

The airflow meter potentiometer can cause problems with the idle control. You need to get closed loop control also, maybe first. I don't remeber the actual symptom we are working with.

The .88v reading is a rich reading. Its either right or wrong. You should adjust the fuel mixture lean counterclockwise till it runs bad or till the voltage drops on the sensor. Once the voltage drops to .6 or less the control can take over. The EHA current should be around 0-3ma (usually right around 0 but I have seen them creap a bit) with the sensor disconnected. If you hook up that .88v sensor the current should go negative up to 12-13ma trying to lean it out. It will succeed if the mixture is lean enough. But it only has so much capability.

On the airflow potentiometer, I look at the resultant output voltage. This is what the computer sees and is such because the computer is in the circuit. The usual voltage around idle is about 1v (.7 to over 1v could be I don't recall) but the important thing is that it stays constant with reguard to airflow plate position. This can be tested with the engine off and the key on.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

steve
when i turn the mix screw ccwise to try and get the reading low the engine runs real bad with a miss bad hesitation and pops at times engine shakes like running on 5 cylinder

steve the problem was the fuel distributor
now whats the best to set the air/fuel mixture for economy/performance. do it at idle or at 2000rpm thanks jose

When everything is right the settings should be the same at idle and at 2000 rpm. The cycle rich/lean/rich/lean/etc will be faster at 2000rpms.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician