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1996, A124, E320 Sportline Cabriolet x 2
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1,555 Posts
Got it, thank you kindly Gents, gives me food for thought. Must have a look at the manual I have here and see if anything is mentioned. Thing is I have a Euro spec car and a late model one at that, [that sticker carries a 210 part number] I have no cats and an independent fuel mixture pot so she’s all a bit different than the manual. Goes like heck though! :):)

Might take a while to get it back on the machine, it's a 1000 km journey in all, but when I do I'll post the numbers and the MPG if you like...??

Makes me wonder if I have backed the fuel mixture off so far that the car cannot richen any more, and I might be doing this to stop it from runing too rich otherwise, MAP sensor is the MAF; is that right Gents...?? I'm ready to start replacing stuff.
 

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Banned
1993 400E
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7,361 Posts
given that , at 2% excess air we should have a reasonably clean burn, with maybe 500 ppm CO (monoxide)
Given the spec for a Euro non cat car is 1.0% +-0.5% I don't see a
reading of 500ppm. Maybe on a US current emissions laden car.

1.0% is 10,000 ppm which is his spec, 500ppm would be 0.05%
 

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Banned
1993 400E
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7,361 Posts
Thing is I have a Euro spec car and a late model one at that, [that sticker carries a 210 part number] I have no cats and an independent fuel mixture pot so she’s all a bit different than the manual I have here.
That's because the W210 was introduced in 1996 with a M104 engine.

Same spec in your area for the W210 and your W124.
 

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9 Posts
If I only have access to a CO tester, would just setting it to 1% +/- 0.5% be good enough or do I need to have the other gasses tested?

M104 KE non-cat here.
 

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w124 400E x R129 w210
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419 Posts
Trying to set the idle on this 89 190E 2.6 and it really is annoying.
The duty cycle is set a per specs. and is right on BUT the idle is sometimes as high as 2000rpm and sometimes normal. WHY....what else is there to adjust?
If I punch the gas pedal, in park, sometimes it comes down to normal... 650 to 750...sometimes not.
If I make the fuel adjustment rich...it doesn't do it ( as much) but it stinks.
What else is there to adjust ?
BTW...new Bosch O2 just installed.
 

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1989 300SE EURO
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271 Posts
Trying to set the idle on this 89 190E 2.6 and it really is annoying.
The duty cycle is set a per specs. and is right on BUT the idle is sometimes as high as 2000rpm and sometimes normal. WHY....what else is there to adjust?
If I punch the gas pedal, in park, sometimes it comes down to normal... 650 to 750...sometimes not.
If I make the fuel adjustment rich...it doesn't do it ( as much) but it stinks.
What else is there to adjust ?
BTW...new Bosch O2 just installed.
Two things you should really try - one is to lube all your throttle linkages, the other very important thing is to get the carbon rails of your air mass flow sensor potentiometer cleaned. That for me made all the difference!!! I had some fluctuating RPMs, too, especially while braking which was kind of scary.
Good luck!
 

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Premium Member
'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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10,132 Posts
A bad/faulty potentiometer will seek idle constantly....but not let it sit at 2,000rpm. Occasional high rpm like that can be leaking injectors. If your injectors are dirty or over 100,000 miles, they need replaced. Do the propane test around all your injectors and see what happens.

Kevin
 

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1992 300ce, 3.0, 207,00 mi.
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335 Posts
I troubleshooted a similar problem couple yrs back, it was the WOT micro switch. Easy to ck and jumper to identify if it is the cause. A bad switch will do exactly as you describe. Let us know what you find.
 

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w124 400E x R129 w210
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419 Posts
Removed and cleaned the injectors.
Lubbed the linkage and replaced the WOT switch.
Also replaced the pot. with a good used one that looked almost new.
Idles better and the start is easier but can still be a littler rough for a few seconds or the idle will go to 1200.
A quick tap on the accelerator pedal will bring it down...almost like an auto choke is on...which there isn't.
Could be a sticky butterfly or linkage.
Once the idle drops it is steady @650.
Actually runs alot better after adjusting the duty cycle.
Now it's time to sell it.
 

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Depends on the week
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3,725 Posts
A bad/faulty potentiometer will seek idle constantly....but not let it sit at 2,000rpm. Occasional high rpm like that can be leaking injectors. If your injectors are dirty or over 100,000 miles, they need replaced. Do the propane test around all your injectors and see what happens.

Kevin
Yes it will. :thumbsup: I spent a few weeks testing and tracing the issue before I came up onto the potentiometer.

As demonstrated by one of my 5 speed mercs.

https://www.youtube.com/watch?v=0rQDReKmOx0
 

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Premium Member
'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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10,132 Posts
Yes it will. :thumbsup: I spent a few weeks testing and tracing the issue before I came up onto the potentiometer.

As demonstrated by one of my 5 speed mercs.

https://www.youtube.com/watch?v=0rQDReKmOx0
I think that must be a very worn/gouged out potentiometer then. Did you take a pic of the arc track that has the wear? I think on the whole, that's a pretty unusual symptom to be traced back to just the air flow potentiometer. But given the age of these things, maybe we should all take them apart and look at the condition...take pics etc. Mine is hunting...no high rpm ever and it's original.

Since the Bosch units cost between $300-$400, I was thinking about the possibility of re-tinning the worn groove with the no-lead, silver bearing solder.....just as an experiment. But I'd have to have one apart in my hand to see the feasibility. If it worked, you could take a Dremel and polish the plate/solder. You've got nothing to loose.....maybe someone could send me a worn out one to experiment with...I'll pay the postage?

Kevin
 

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Depends on the week
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3,725 Posts
I think that must be a very worn/gouged out potentiometer then. Did you take a pic of the arc track that has the wear? I think on the whole, that's a pretty unusual symptom to be traced back to just the air flow potentiometer. But given the age of these things, maybe we should all take them apart and look at the condition...take pics etc. Mine is hunting...no high rpm ever and it's original.

Since the Bosch units cost between $300-$400, I was thinking about the possibility of re-tinning the worn groove with the no-lead, silver bearing solder.....just as an experiment. But I'd have to have one apart in my hand to see the feasibility. If it worked, you could take a Dremel and polish the plate/solder. You've got nothing to loose.....maybe someone could send me a worn out one to experiment with...I'll pay the postage?

Kevin
Nope, I simply adjusted it. Seemed as if someone was messing around in that area anyhow as it was missing one of its screw covers. However, IIRC, it was only about .15v off of where it should have been. It had me scratching my head for the longest time because similar mileage M103's I've had hadn't had any issues with potentiometers.
 

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1985 SL 380
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7 Posts
Hey folks! I have read this post from beginning to end. I must say there is great information with plenty of detail. My father also has a 1985 380 SL that is in need of an adjustment to the air/fuel mixture. I am using the voltmeter method as I do not have a DMM with duty cycle feature. When trying to adjust the air/fuel mixture this weekend I did not observe the behavior I had expected to see with the volt meter.

Here are the steps I performed to show what I did and confirm my understanding:

1) Started the car and let it get to operating temp.
2) found the x11 connector.
3) checked battery voltage by - red lead in #6 and blk lead in #2 . Reading was 12.89
4) inserted red lead to #3 and blk lead to #2 .

At step 4 I was expecting the see the volts oscillate between two values. What I observed was a static volt reading of 12.55. No variance. Adjusting the Lambda may no change in the voltage reading.


Noteworthy information about the car:
1) Recently replaced the idle control valve
2) While trying to adjust the air/fuel mixture and noting to my Father that I was not seeing the behavior I was expecting with the voltmeter, I mentioned that I thought I had read this behavior may point to a bad O2 sensor. That's when he told me the O2 sensor had been removed when the exhaust had been replaced.


Questions:

1) Would the elimination of the O2 sensor cause the volt reading to be static verse the oscillation be tween to voltage points?

2) Is there another method by which I can adjust the air/fuel mixture?
 

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Premium Member
'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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10,132 Posts
Your voltage fluctuates up and down and equal amount because of the O2 sensor and its heater. That's an integral part in the lambda loop on the 124 cars. This forum is for 124 cars.

Keviin
 

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Premium Member
1993 300CE Cabriolet (mine) ; 1994 E320 Wagon (wife's) ; 1990 Benz 300E 2.6 (son's)
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6,748 Posts
without an o2 sensor, the only way to set the mixture is with a exhaust gas meter, connected to the test port before the catalytic converter.
 

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1985 SL 380
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7 Posts
Understand this is a thread on the W124, but thought I had seen some posts from 107 owners as well where this process worked for them.
 

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W124 Moderator
86 190E 2.3L 16V, 2 95 320TE's, 02 S500
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12,633 Posts
Bottom line is that you need an O2 sensors reinstalled. It will require taking the car to a muffler shop and having a bung welded in.
 

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190e 1.8l 1992 petrol
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17 Posts
After a quick test of km/l i got this fuel consumption

23% richer = 4,8mil / 3.4liter 0.71
45% leaner = 4,8mil / 5liter 1

Car responds better is stronger and lower consumption on 23%.

MyCar, 190e 1.8l 1992
 

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Premium Member
1993 300CE Cabriolet (mine) ; 1994 E320 Wagon (wife's) ; 1990 Benz 300E 2.6 (son's)
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6,748 Posts
the standard metric fuel consumption measurement is liters per 100km, while the imperial measurement is miles per gallon. I'm not familiar with your notation of N mil/ M liter...

its very hard to get accurate fuel consumption readings over short distances without using laboratory equipment such as a graduated cylinder instead of the fuel tank. the defacto method of fuel economy is to completely fill the tank, drive a significant distance, then refill the tank to the same level. I find different fuel pumps will shut off the gas +/- several liters of nominal full, so you really need to average several tanks... and of course driving condtiions can make a 50% variation or more in your fuel economy.

my 300CE Cabriolet (3.2L M104 HFM-SFI, so really its a E320) has gotten between 9.75 to 15.5 l/100km, or between 24 and 15 Miles/US gallon, depending on where and how I'm driving.
 
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