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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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It is EHA current, not voltage, which makes it a bit trickier for most but you'll do fine Laura. Hopefully you will not need it.
The thing about the EHA current is, it is where all the sensors, actuators finally funnel into, that one final actuator.
So if that is not correct, you know it is a problem in your emission system.
 

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1990 Mercedes Benz 190E 2.6
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Discussion Starter #22 (Edited)
Well had a chance to putter before my grandson comes over for the weekend.

Residual fuel pressure after 18.5 hrs. - 1.1 Bar

4 pin temp sensor 5150 ohms at 2C
2500 ". ". 70C
EHA 60% @ 2C } unplugged
69 % @ warmed up engine } unplugged
10% but jumping a little up and down when plugged cold or warm
These were measured from the 3 and 2 pins of the diagnostic plug on the drivers side fender.
I did measure the milamps at the two pins closest to the EHA and the reading was 25 but difficult to measure temp because while engine was quite warm with the hood up the air temperature was much colder. I hope this helps.
.
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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3,698 Posts
Residual fuel pressure after 18.5 hrs. - 1.1 Bar
We knew you have this issue, probably does not effect your running issue. Check

4 pin temp sensor 5150 ohms at 2C
Check

2500 ". ". 70C
Not following this
2500 ohms @ 70C ????

EHA 60% @ 2C } unplugged
69 % @ warmed up engine } unplugged
69% read at the meter (which defined by Mercedes as 31%) ????. What is unplugged??

10% but jumping a little up and down when plugged cold or warm
10% duty cycle?? Anything unplugged?

When you are measuring duty cycle do not unplug anything even though some sources say the check valve at the charcoal canister splitter should be plugged. Makes no difference, as long as the system is working.
 

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Discussion Starter #24 (Edited)
I guess I am having trouble either with reading the multimeter or maybe it needs battery? Working in the cold may be a factor as well.
The warm ohm reading on the 4 pin sensor might be 250 @ 70 using the temperature gauge on the car. Would that seem right? By unplugged. I mean the 4 pin from the EHA.
It seems to read 69% when the EHA is unplugged from the sensor and around 10% and wandering when it is plugged in and engine warm.
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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3,698 Posts
Let us make sure you can make the thermistor resistance readings consistently and correctly before we graduate to EHA current Laura. That is a bit more difficult. And you will need 3-cables with alligators clips for that. It is futile if you do not have the wires.

Make sure your readings match my readings on the resistance first please.

We will tackle EHA current while cold next.
 

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Discussion Starter #26
Dolucasi, I am sorry I messed this up. I was in a hurry with the grand child coming. The plug that I unplugged was the 4 pin one for the CSV! Stupid of me. Tomorrow I will take my time and get this right with a new battery in the Multimeter. The cold car start nstantly then died but with the gauge hooked up so no CVS to help and then it wouldnt start obviously without the shot of gas from the CVS. I wonder if the injector(s) is/ are leaking gas. I have a few of the alligator clips laing about in the garage so I will be interested in testing the EHA valve. Should I check the duty cycle both cold and warm. I will do another test of the 4 pin thermo sensor and the air sensor on the air filter housing.
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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No worries. If you had a problem there we would have known about it a long time ago.

Just measure all the relevant temp sensors and report on those at cold and after the car warms up.

(1) Intake air temp sensor
(2) Coolant temp sensor as such:

. 1
2 . 3
. 4

1 to 4 and 2 to 3.

(3) Also measure your static duty cycle (pin 2 to 3) , ignition on, engine off. This may tell us if there is a fault code.
(4) Also start the car and re measure the duty cycle at cold.
 

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W124, 230E 5 speeds Manual, 1987
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Yes, that will give you a false reading for sure. Also do not forget the intake air temp sensor. I believe yours has that (my '89 does not).

I would actually not look into ignition after these. I would measure the EHA current if you can. There you will see the fuel enrichment (if you have any) at cold.
At those temps is should be in the range of +20mA to +30mA for the first 30 seconds or so and will start coming down rapidly, linearly with coolant temp rising all the way down to near 0mA.

But let's take this one step at a time.
Measuring the EHA current is a must. But i have a little suggestion to rule out the possibility of condensation inside the distributor cap as it may happen at that temp variation.
@LauraS try to heat the distributor cap a little with the hairdryer before.starting the car and see what happens.
 

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Discussion Starter #29
OK! thanks for the advice. -13c this morning so good temp to check.
 

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Discussion Starter #30 (Edited)
OK The results: Ambient Air Temperature -4C @ Engine Cold
Ignition on:
Air Sensor 5830ohms
4 Pin Sensor 1-4 5990
2-3 5990
Diagnostic plug 7.92 Volts with battery at 11.9 Volts
69.9% Duty Cycle

Engine running warm:
Ambient Air Temperature 0C @ 80-85C engine temperature
Air Sensor-
4 Pin Sensor 1-4 250
2-3 248

Diagnostic Plug 1.47volts with battery charging at 13.6 Volts
9.9-10.1 % fluctuating rapidly @700rpm
9.1 - 10.1 %. ". ". @ 2500rpm
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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3,698 Posts
OK The results: Ambient Air Temperature -4C @ Engine Cold
Ignition on:
Air Sensor 5830ohms
4 Pin Sensor 1-4 5990
2-3 5990
Diagnostic plug 7.92 Volts with battery at 11.9 Volts
69.9% Duty Cycle
Check, Check and Check.
69.9% DMM duty cycle = 30.1% Mercedes Duty Cycle
ECU is telling you things seems to be in order for what it can report from the X11 port

Engine running warm:
Ambient Air Temperature 0C @ 80-85C engine temperature
Air Sensor-
4 Pin Sensor 1-4 250
2-3 248
Check, check and check - I assume Air sensor still remained in the high 4-5K range

Diagnostic Plug 1.47volts with battery charging at 13.6 Volts
9.9-10.1 % fluctuating rapidly @700rpm
9.1 - 10.1 %. ". ". @ 2500rpm
Hmm, this is weird. You actually have an issue here. Meaning your lambda adjustment is way out of whack or something else is wrong like the O2 sensor loop.
10% DMM Duty cycle (90% Mercedes Duty cycle) at operating temp, your ECU is having to enrich the mixture almost all the way to it's limit.

If the oxygen sensor is good, your engine is starving for fuel and potentially this may cause you trouble in cold starts.
Because the cold mixture is pre-set, O2 sensor is not in the loop and it forces a fixed enrichment based on the ambient and coolant air temp.

So now we have to figure out what is wrong with your lambda mixture at operating temp. If we correct that, there maybe a change the cold issue goes away.

(1) Has anyone tempered with your Lambda Adjustment screw before? Can you give a history on that.
(2) And remind us what is the mileage on the engine (and O2 sensor).
(3) I suppose there could also be unmetered air getting in the system that is not metered by the AFM plate (and therefore the FD)
(4) How is the pick up on the engine when warm? Is it a bit sluggish.

At this point we do not need an EHA current measurement, let's assume that the ECU is correctly translating the EHA current to the duty cycle signal.
 

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Discussion Starter #32 (Edited)
All very interesting. To my knowledge the Lambda adjustment hasn't been touch. It might have been when my husband was here since he looked after the cars but that was several years ago and the car has never acted like this before until this recent cold weather arrived.
From what I have been reading the O2 sensor doesn't enter the loop until the engine warms so why would it affect the cold start? The catalytic converter was changed about 15000km ago and maybe the 02 sensor ? It was expensive! The car has a total of 129000km since new.
Once the car starts there is no hesitation and can be driven with no problems. The acceleration is excellent.
The symptoms seem to be either a lack of fuel or too much and since this began only after the temperatures dropped it is more likely lack of fuel? Would you agree? So how do I adjust the Lambda or EHA to allow for more fuel when the engine is cold if that is your opinion? Where should the duty cycle be when warm and how do we get there.
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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You should not adjust anything just yet. This is why I asked the particulars.
Your engine is way too young at ~80K miles to have any issues like this.
355, PN187 and I were just commenting on how little emissions issues we have had between the four ~200K mile old W201's we have. All M103 engines.

Can you please:

(1) See if the adjustment tower has been tampered with. To make the first adjustment, the top of it needs to be hacked off to gain access to the adjustment screw. I doubt yours has been touched.
(2) Have you seen video's from Kent Bergsma (Mercedes Source), particularly about "code reading". If not please google it and watch that video. If your 9 pin diagnostic port (shown in the video) has an led on it, that will be great. In '89 only CA cars had that. Not sure about '90. If you do not have the led it will be difficult as we would need a simple code reader.

That diagnostic port could report some other issues, though some of these codes also throws the check engine light, and you do not have that. In any case it would have been good to know.

(3) For your duty cycle being off when warm, we should make oxygen sensor readings. This is pretty easy, when ready either search online on how, or ask in this thread and either I or someone else will help you.

If your mixture adjustment is truly off by so much, I'm not shocked that it is showing up the most when engine is cold and the weather is bone chilling.
I will explain that later if you would like me to but in a nutshell, the emissions can correct for it being off when the O2 sensor loop is working (up to a certain point)
It can not when it is not working (cold) , and you are already at the limit of enrichment for the EHA, there is very little room for it to go beyond that, therefore when cold your mixture is too lean.
This is my theory anyway, it is yet to be proven.

- Cheers!
 

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Discussion Starter #34 (Edited)
I will look at the FD tower tomorrow to see if the top is knocked off but I seem to think that there is a hole open at the top. I seem to recall that several years ago my husband took it to a local garage for servicing since the dealer was so far away and the mechanic did some work on the engine but I don't know what. This was before we had internet service otherwise my husband would have never taken his car to another mechanic so it must have been something he couldn't adjust or fix himself. He was a commercial pilot and aircraft engineer and serviced our aircraft.
Thete is no led light on the 9 pin diagnostic port if you mean the flat black panel with the white numbers on the battery side of the car. I will do some reading on how to test the O2 sensor. I really am scared to touch the FD or EHA adjustments but will it I have guidance so stay with me on this and I am sure we will get it right. So you think the starting cold issue is a too lean mixture?
You must be getting tired of me being such a nuisance.
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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No trouble at all. No worries.

I'm not sure how many Km's the car had when that tower was broken into but it sounds suspect as that is intended to be a near permanent setting.
Surely a car like mine at 200K miles, one would expect that but yours?
The car was quite young it seems when it was adjusted, so it could have been a mis-diagnosis, but we will never know.

(1) Since you do not have the LED let us not chase other fault codes, since the check engine light is not on. However, it works correct? When the ignition is on engine off it lights up?
Then it goes off after you start the engine?

(2) Yeah, when it is a little warmer, go ahead and measure your O2 sensor. It is expected to cycle between a low voltage (near zero) and a higher voltage (like 1 volt). Periodically (one or two seconds).

(3) BTW, when was the last time you measured your duty cycle and it was fine?
 

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Discussion Starter #36 (Edited)
To answer your questions;
CEL goes in with ignition
CEL goes out with start up
The last time that the Duty Cycle was checked and was correct was when we were discussing the fuel pressures a short while ago possibly early October.
This issue only started when the temperature changed about two weeks ago. Once I changed the EZL it was working fine.

My grandson helped me with the car this weekend and is keen for me to give it to him or perhaps his father. I just may do that.
A Toyota Rav 4 would look good on me!
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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That info confirms to us that your lambda adjustment screw is just fine the way it is, and perhaps my guess that it is off and effects your cold behavior may be incorrect.
It is not going to be off like that in a few months after you confirmed it was fine.

I would do the O2 sensor measurement next. The O2 sensor should not effect your cold issues as far as I know. This is just to figure out why it is so off when hot.

There are only a couple of sensors left to check on the car after the O2 sensor and they are not temperature related. Puzzling.

One component I'm not familiar with because it does not exist on a '89 is the EGR valve. Wondering if something is wrong with it. I would not know how to diagnose that.

Great that your grandson would like the car.
 

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This has certainly been an absolutely baffling problem and I agree that it's happening at a mileage it shouldn't be happening at. Issues like this where everything seems to be what it's supposed to be used to drive my engineer father absolutely crazy and they usually wind up being some silly little thing that had already been checked. On that note, have you checked all of the wiring connections to make sure they're nice and tight and clean? Maybe the fuel filter or fuel lines are partially blocked and the cold start is clearing this partial blockage to the point that the car runs fine when it's warm? These kings of issues can be a real stinker to diagnose. I'm kind of at a loss at this point as to what else to suggest. You might also check out some of the Pierre Hedary online videos too to see if he's addressed this issue. He actually owns a W201 as well as a repair shop that specializes in this era of MB. It might also be worth it to contact the MB Classic Center, explain your car's symptoms and the testing you've done to try to diagnose the problem and see what they have to say.
 

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Discussion Starter #39 (Edited)
w201fan and Dolucasi, Thanks for the advice. I will check every connection that I can find and the fuses also just to be sure. I know that last winter a mouse had tried to build a nest under the air cleaner while that car sat for a few weeks while i was in southern France on a holiday. A couple of wires had been chewed although just the insulation as far as I could tell. I taped them back up. They are a bit hard to get to but perhaps I missed one. Would a wire to the EHA make any difference if it was broken. I know during my tests that there was no difference when I unplugged the harness to the EHA?
Not a bad day today in the + 5 range and the car did seem to start a bit easier on about the 3rd try.
I forgot to mention. The top of the tower has been removed and the little screw is visible. Someone must have felt the need to adjust it I guess.
 

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Discussion Starter #40
I have bothered you folks enough. I am just too old to be trying to keep this old car on the road. I have decided to take it off the road for the winter. I will store it without the battery and cover the body. My grandson wantsit and when he gets his licence he can play with it. I will have to buy another daily driver and my daughter and her husband are going to look for something more modern but it wont be the same as have a classic Mercedes. Thanks for all your patience and help over these many months. I will miss the repartee.
 
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