I think it's clockwise to enrich, and ccw to lean.

 

Lean is CCW. I did this same adjustment on my 86 300E. I went 1/2 turn to lean and it made all the difference in the world to the initial acceleration. Felt like getting 50 hp. Use a long shank 3mm allen. It is spring loaded, so push down until it bottoms out.

I also picked up more than 1 mpg in town. I now average almost 24 under normal driving. A bit better than 26 on the highway at 85 mph.

good luck,

jayare

 

Obrigado meu amigo. Fiz a mesma coisa e meu carro, (1990, 300CE24) mudou de áspero e desagradável para um gatinho manso. A performance também melhorou muito. Translation: Thank you very much friend. I did the same thing and my car, (1990, 300CE24), went from rough and unpleasant to a tame kitten. Performance has improved a lot.

 

If you push down to far the engine will cut out! You just want to push down enogh to engage the screw underneath the plunger with the engine running. You need to monitor pin 3 of the diagnostic socket using a duty cycle multimeter and get it to 45-50% duty cycle.

 

You need to monitor pin 3 of the diagnostic socket using a duty cycle multimeter and get it to 45-50% duty cycle.

This is not the correct information, as you can see from the WIS screen shot
above, Mercedes calls for oscillation from 35% to 45% for a 40% average.

At 2500rpm, you should be within 10% of the idle reading.

Remember to plug the purge valve vac line.

 

Yal, if possible, I'd like to adjust the mixture on my E320. I'm getting a code that tells me the Lambda is out of limits. Can you tell me where the adjuster is for the E320, and how to measure the duty cycle? I have access to a fluke multimeter.

 

Made the adjustment using the multimeter and the car runs like brand new, thanks for the advice.

 

Will this work the same on a 230E?

 

can you tell me how you used the meter to monitor duty cycle? what was your car doing that made you think it needed adj?

 

Mountain,

I'll PM you tomorrow with the multimeter model number I purchased from Sears. It was less than $40 bucks. You need a meter that has a duty cycle feature.

Jayare

 

Would a dwell meter do the same measurement as a duty cycle meter?

 

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Actually I was checking all vacuum hoses and found a crack one, I can not ID for you though. As far as the adjustment is concerned, this was previously posted by member Yal. ( Thanks Yal !!) Do an additional search under idle mixture or fuel distributor adjustment and you should be good to go. This forum is a great source for maintaining and trouble shooting

Its pretty simple. Now it may not be the cause of your problem but its a good start. What you need however is a multimeter from sears that reads duty cycle as a %. Real cheap cost about $30-40, and invaluable Sears.com 482139000. Then you need a set of allen keys, I believe the adjustment nut is #3 allen size but I am not sure, I just bought a set of them. Take of your air cleaner and you'll see a "steel" tower next to the fuel distributor. The adjustment nut is located inside at the bottom of that tower. Now you have to locate the x11 connector on the driver side fire wall. Its basically a round socket. It looks like something should be plugged into it. Its usually covered with a plastic screw cap.
With the car running and warmed up and your mutimeter set to duty cycle stick the positive terminal into the number 3 hole of the x11 connector and ground the negative terminal. I usually stick the negative on a strut support bolt next to the driver side hood hinge.
Then watch the duty cycle. If its not swinging back and forth make sure you selected % by pressing one of the selectors at the top of the multimeter (took me forever to figure this out).
The duty cycle should fluctuate around 50%, if it doesn't you have to adjust the screw at the bottom of the tower until it does. If I remember correctly clockwise brings it up and anti clockwise vice versa. Adjust by small increments and wait 10 seconds each time. The screw is spring loaded and so you have to depress it a little to get it to engage before turning. If you depress it to far the car will cut off.
Thats it.
It could turn out that all you need is a fuel filter change

If you do this let me know what you find. You can check the same thing from the EHA which is a little black box at the back of the fuel distributer but you need a test harness for this.

 

thanks for your info. i have a fluke MM at work. does it have this setting? what would the icon for duty cycle look like on the meter?

 

Mountain,

Everything GHM is stating is right on the money. My Sears multi meter is Model #82400. Has the duty cycle setting, punch the % button and it's reading properly. Also, the unit comes with a temp probe..

On the metric allen wrenches... I purchased a long handle set from Granger. That way, I don't have to remove the air cleaner housing to adjust the mixture. Wrench goes through the hole in the center of the housing top. The adjuster "tower" came from the factory with a steel ball fixed in the top to keep us types from tampering with the adjustment.

In my case, a slight tweak to the lean side (ccw) made my first W124 (86 300E) smooth out, idle like a sewing machine and have instant throttle response. Same goes for my coupe which has the M104 motor.

I to, have a bit of a warm/hot start problem if the car is left alone for 10 min. after running. I discovered that my fuel line from the tank to the filter is leaking "sweating" as it were. Picked up a new line from the dealer yesterday and will install it this weekend. I'll let you know if it is the culprit.

Good Luck,

Jayare

 

hey jay,
thanks for all your input during my troubles. i will look at my local sears for this meter. just in case my adj. goes screwy for some reason, what would the meter be reading like if the O2 sensor was bad? that way i will know before i come back to the forum and ask this question. also, what made you want to adj. your air/fuel? was it running rich? poor acceleration? etc. i have yet to drive wifes 260e since i fixed the hot start prob. today. but last time i drove it, it was a real dog on acceleration. i think my diesel maybe could have outrun it. would tweeking the air fuel make a big difference?

 

any info would be very helpful




hello, i have been trying to adjust my fuel air mixture on my 89 300ce 3.0 because of very high levels of un burnt gas in the exhaust during an emissions test. after finding a multi meter with the ability to test duty cycle. i hooked it up with the red probe in the #3 test terminal and the black probe in #2 . it is supposed to be at 70% ignition on but engine not running from what i understand. well mine is at 95.8? when i turn the engine on the reading for the duty cycle that is supposed to be around 50% drops to 0 and i get no reading at all. The adjustment screw was messed with by the previous owner and i adjusted it to extremes to see if i could get anything to show up on the meter. the part that i do not understand is that when i adjust the screw i see no difference in performance at all. no change in idle speed, or anything for that matter. Not knowing what they did to the car is difficult but i feel like i should be getting a reading. through my research this signal to the #3 plug terminal comes from the O2 sensor? so would the out of wack reading in the ignition on position and the no reading during idle be caused by a failed O2 sensor? or should i start looking more towards the fuel distributor. any tips or reply is much appreciated, im trying to get this baby benz back on the road and happy

 

A slight adjustment with the fuel/air mixture will compensate for age and wear/tear. My old sedan was also a dog upon initial accel. After leaning it out a bit, it was like getting 50 extra hp. An amazing difference. I don't have the knowledge bank to answer your question about the O2 sensor reading. The OEM unit is rather expensive. The connectors for it are under the carpet on the passenger side up against the tranny tunnel. You should see "blue" sheathing over the wires. On my M104, it is a 3 wire sensor. I replaced it with one from a 90 5.0L Mustang. Spliced the MB connections and was on my way. I want to remember that the two wire sensor can be from a 3.0L Chrysler Mini Van.

When I made my initial "lean" adjustment on the M103, the engine smoothed out and the idle in drive was dead perfect. No vibrations whatsoever. Just remember that the adjustments should be made in very slight increments. Maybe 1/8 - 1/4 turn at a time. Also, remember where you started from in case you have to go back that way.

Good Luck,

Jayare

 

hey guys, i got my MM at sears last nite. they discontinued the 82400. but i found one even a little cheaper that test duty cycle. so i should be good to go. wife is at a cleaning job now and i will check it out when she returns.

 

guys, initial testing, warm engine at idle showed 82.5% i adjusted the screw and got it varying between 48-53% is this OK? it did not improve idle that i can tell. i will drive later and see if anything improves. thanks

 

I would be carfull and not lean it out to much...I will be doing this also in the next few days....now reason why you should not lean it out to much is because you may burn out your Catalitic converter.

 

Just in the range you want to be. You won't notice any idle speed increase/decrease. Maybe a bit smoother however. Let us know how the adjustment worked out. Your "off the line" response should have improved.

Good Luck,

Jayare

guys, initial testing, warm engine at idle showed 82.5% i adjusted the screw and got it varying between 48-53% is this OK? it did not improve idle that i can tell. i will drive later and see if anything improves. thanks

 

hey jay, wife says the response is alot better now. i took it for a wide open mountain run the night after i did the adj. and it did seem like it was faster somehow. i do not drive it everyday like she does so i really could not tell. she says all is well though. thanks to all who helped.

 

Mountain,

As long as Mama is happy, then you are happy. Glad it all worked out.

Jayare

 

aint that the truth....

 

Hey,

I wanna try this on my 1991 230CE, but I have 2 questions:

- My X11 connector has less pins, if I recall correctly... 9 pins? Can I still use the #3 for this adjustment?

- The tower with the adjustment screw has a yellow cap on top... Is this removable? Or should I just press it in and turn?


Thanks

MR

 

Hey,

I wanna try this on my 1991 230CE, but I have 2 questions:

- My X11 connector has less pins, if I recall correctly... 9 pins? Can I still use the #3 for this adjustment?

- The tower with the adjustment screw has a yellow cap on top... Is this removable? Or should I just press it in and turn?


Thanks

MR

anyone?

 

Well,

I found out that my 9 pin connector has the same function on pin #3... That's cool.

But I'm still puzzled about the yellow cap/protection on the top of the adjustment screw / tower...

Did anyone had to remove it?

 

I haven't seen a yellow rubber cap, but that would limit your ability to get an allen wrench down the tube to the adjustment screw. I'm fairly sure the cap should be removed and it is just there in place of the bearing that usually blocks access to this adjustment.

 

Yes, you have to remove that plastic yellow cap.
I have pierced it with a small screwdriver and then I have extracted it