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Old 07-05-2003, 09:50 AM
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Join Date: Oct 2002
Location: Toronto, Canada
Posts: 700
multimeter and O2


I disconnected the O2, plugged one contact of the mm to it and the other to any ground, if I remember correctly, it'll show you the readings, if you get negative ones, just switch the contacts. The O2 does not create any current flow, just a potential difference. If you have a digital multimeter you can just use it as an extension of the O2 between it's connections and it will show you the voltage as well, only digital ones will do this because they have to convert resistance and current to voltage. I did it this way to test it on the road, worked like a charm, but after adjusting the mixture I found that the O2 would not bottom out at 0V, still trying to correct that but I think I would have to take the car to the dealer and get it adjusted with some serious machinery, for now it runs fine gets me where I want to go, so all is well.

great car now that I fixed most of it's problems. Just this morning I was doing a highway ramp at 60kmph, it was a preatty steep curve and the car handled like a rock, can't ask for more then that out of something so old


Down with new cars!!!
1985 190E 2.3L - a constant project.
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Old 07-05-2003, 10:27 AM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
Where you hook the volt meter depends on what you want to see. If you wish to see system performance one must monitor the voltage with the O2 sensor hooked to the system.

Measuring the open circuit value is only of use in determining whether the sensor CAN work and in determining whether mixture is VERY rich or VERY lean.

If the car runs in closed loop it is probably very close to right. Closed loop can only be established with the sensor in the system by definition of "closed loop"
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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Old 07-06-2003, 06:50 PM
Registered User
Join Date: Jan 2003
Location: Near Detroit
Posts: 19
you don't need the sensor to go to 0.0V, it's only a switch. If it drops below .5V, you're lean, when you're above .5V you're rich. Typical values are 0.1-0.9. It doesn't matter if you're at 0.1 or 0.3, nor 0.8 vs 0.9, only above or below 0.5V matters.
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Old 07-06-2003, 11:57 PM
Posts: n/a
I would like to hook up my multimeter to the EHA.

It has 2 contacts, so do I connect my MM in series with either one of the contacts to read the EHA current?
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Old 07-07-2003, 12:30 AM
Posts: n/a
I am learning...

Steve Brotherton

You wrote :

You have given us little more than to say your car is broken and ask what is wrong. I don't wish to be negative, but it is insulting to think that people think automotive technology is so easy. No wonder people think auto repair cost too much. Listen to simple description of problem, move car to shop, wave ones hand, and come out with a big bill. I'd be pi**ed too.

I want to have somewhat of an idea of what's wrong (if that is possible in this case)... obviously only guessing by symptoms... before having someone work on my car.

No offence intended.

Everyday, I am learning more about my car from this forum, and you are one of the "Jedi Masters" on this forum.

My apologies if my post has caused you to feel insulted.

Sunil - I have not made any adjustments to the mixture prior to the symptoms.All the components you mentioned have been checked and in fact, recently renewed.Your comments with regards to the cold start valve make sense. I believe the cold start valve is controlled by a thermo time device.

Anyway, I am having the car taken to my indie for transmission problems.I will ask him to sort this issue for me.

In any case, I would be interested to know how to setup my digital multimeter to read the EHA current.

My kid bro's 190e seems to be running a little rich and we would like to check on it with my MM.

Thanks for all your help, guys.
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Old 07-13-2003, 09:26 AM
Posts: n/a
I got my car back from the indie with the tranny rebuilt.

He said he adjusted the mixture slightly to correct my problem, but also mentioned that the problem was attributed to my fuel distributor, which he says is going bad.

Doesn't make sense to me.

My car only misbehaves when it is warm.

If it were the fuel distr, then the car would be bad at all temps and not only warm.

After warming the engine, I pulled off the cold start valve and it did not make a difference to the idle (heavy exhaust).So it went right back in.

I disconnected the EHA from the system and it seems to idle better (seat of pants meter).

I also pulled out a round 4-pronged sensor (next to the clutch fan sensor) and the tip was dirty so I cleaned it up and put it back in. The sensor prong seems to be immersed in water (in the block).

I don't exactly know the function of this sensor but I guess cleaning any sensor is GOOD...

Then, I went out for a run in my car (with the EHA disconnected).

Usually (with the current problem), I have to drive in S mode to overcome the severe hesitation (even then, slight hesitation) from stop, and then when I get to accelerate (slingshot effect), I leave behind a trail of black smoke!

Hesitation gone (thank you Captain Obvious!) in S mode.Switched back to E mode and no hesitation!

Also, from the headlights of the vehicles behind me, I don't see any trail of black smoke at all!

I will have a longer run tomorrow afternoon (now it's at night) to confirm the above results. Also, I will start to monitor the mpg.

I used to get 420km before my fuel indicator lit up. With this problem, I only get to 290km on a full tank!

If it all seems ok, the mechanics are ok, if not good.

Then, next I would have to look at the closed loop system.

My car has no cat, hence no O2 sensor.

Anyone know what i need to check against the EHA current values?

Thanks in advance, guys.
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Old 07-13-2003, 11:17 AM
Posts: n/a
With the EHA off, would I face any cold-start issues?

Rough cold idle?
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