Welcome Guest [Log In] [Register]
Photobucket
Welcome to Mercedes-190.co.uk

We are the Mercedes 190 owners forum, the place to be for all owners and fans of the Mercedes 190E, 190 and 190D cars. Including Cosworth (2.3 16v and 2.5 16v), EVO 1 and EVO 2 models. Modified and concourse, track cars and daily drivers, all are welcome.

This free UK based forum was started back in November 2005 to serve the Mercedes 190 W201 community and now has over 9000 members from all around the world and 600,000 + posts.

The members welcome you and encourage you to stay a while and have a look around.
We offer you friendly chat and access to some very useful information as well as tutorials with photos and videos for many common repair and maintenance jobs.
Whatever your needs there is a good chance you will be able to find what your looking for. Such as our Mercedes 190 buyers guide

Sign up to gain access to all areas including for sale / classified areas and country wide meetings and events. Many forum features and sections are only available once you sign up.

Join our forum at mercedes-190.co.uk!

If you're already a member please log in to your account:

**New members signing up**
please check your junk mail for the email authorization email
otherwise we cannot verify your new account.
I have noticed a lot of unauthorized accounts in the system.
Regards
Admin

Username:   Password:
Add Reply
*Mixture and EHA Adjustment Guide*
Topic Started: Sun May 9, 2010 5:47 pm (6,745 Views)
stuu
Part of things
[ *  * ]
So after countless hours of research I've come across loads of different pieces of information online on how to adjust the mixture and EHA. I know there are loads of guides already online but this one is a collaboration of various info from different people and I've changed certain aspects and hopefully saved loads of people from trawling online for hours like i did!

Anyway, I'm not sure if its of any use to you guys but it was to me so here it is:

Required: Multimeter with duty cycle.

1. Remove air cleaner and unscrew the cover of the diagnostic socket on the fender (on the fuel/ignition box there).
2. Set the meter for duty cycle and put the red probe in the #3 hole and the black probe in the #2 hole in the diagnostic socket.
3. Switch ignition on but do not start engine. Should read 70%.
4. Start engine. Duty cycle will be 50% until the oxygen sensor warms up, at which point it will go way down to 30% or less if you are running rich and the electronics are working. Let the car idle and heat up to 80C.
5. When the computer is controlling the mixture, it will read something other than 50% and will change all the time. At this point, you can use a 3mm Allen wrench to adjust the mechanical fuel mixture at the fuel distributor. Insert Allen, then press down GENTLY to engage the key in the screw. Don't press very hard, you will shove the mass flow sensor flap down and add extra fuel.
6. Clockwise is richer, Counter clockwise is lean, only turn in SMALL amounts.
7. Turn the Allen slowly and release the pressure, then wait a bit to see where the reading goes. At idle it will take 10 sec or so for the change to show up, and if you get carried away, you will have trouble getting the correct reading.
8. Adjust in small increments, 1/16 turn or so at a time, until you get a reading close to 50% duty cycle. This should set the EHA current at close to 0, giving you proper fuel mixture control.
9. Now, the fun starts. If you cannot obtain anything but 50% duty cycle with no changes, the O2 sensor is bad or unhooked (connector is under the floor mat in front of the passenger side front seat). If it changes, but you cannot set it to 50%, something else is wrong.
10. You should get momentary enrichment (lower duty cycle %) when you open the throttle, going back to 50% quickly. If you get the opposite, you probably have a bad mass air flow potentiometer, so the computer doesn't get signaled you opened the throttle.
11. Your car should now be around 45-55%. Now rev the motor up to around 2500rpm and it should be 10 less then your idle number %. If not, you need to re-adjust the EHA.
12. The EHA is a small black box located on the side of the fuel distributor. There is a screw in the middle that needs removed and a 2mm Allen key is required. Counter Clockwise is leaner, clockwise is richer.
13. If your car is running say 25% at 2500rpm turn it counter clockwise (to lean it out), if it's like 70% turn it clockwise (to richen it up). It doesn't take much, turn it ONLY A 1/8 AT A TIME. I have mine set to 45%-50% at idle, 38%-40% running at 2500rpm.
14. Get it right and you won't believe how much happier your car is. You have to play with it though cause my numbers won't match yours.

Note:
The lower the % means the car is to rich.
The higher the % means the car is to lean.




Edited by stuu, Sun May 9, 2010 6:01 pm.
Offline Profile Quote Post Goto Top
 
stuu
Part of things
[ *  * ]
Few mistakes sorted, if anyone see's anything incorrect feel free to say.
Offline Profile Quote Post Goto Top
 
highwayman
Member Avatar
Polar bear
[ *  * ]
Can anybody point out a multimeter that DOES have this duty-cycle measurement? Iīve been trying to find out what they might cost to buy, but havenīt found them anyway. Or are you using an oscilloscope to read out the duty-cycle measurements?
Offline Profile Quote Post Goto Top
 
stuu
Part of things
[ *  * ]
Here ya go:
http://www.maplin.co.uk/Module.aspx?ModuleNo=222059&C=Froogle&U=222059&T=Module#checkstore
Offline Profile Quote Post Goto Top
 
cosser
Part of things
[ *  * ]
..
If only I had a pin 3 on my X11.. sigh..lol..!!
Offline Profile Quote Post Goto Top
 
stuu
Part of things
[ *  * ]
lol im adjusting mines today, its running at 80% atm so she's running very lean!
Offline Profile Quote Post Goto Top
 
stwat
Member Avatar


cosser
Wed May 12, 2010 12:25 pm
..
If only I had a pin 3 on my X11.. sigh..lol..!!
Same here :-/
Offline Profile Quote Post Goto Top
 
highlanderian
Part of things
[ *  * ]
wee bit confused, is it dwell angle or duty cycle you have to set the meter to? ibought the maplin one and it has both, there another post about fault codes , he uses dwell.......help pls lol

Offline Profile Quote Post Goto Top
 
kentronix
Member Avatar
I'm only really here for the Kitchens

pretty sure its duty cycle, its the percentage of 'up' time relative to 'down'.
Offline Profile Quote Post Goto Top
 
highlanderian
Part of things
[ *  * ]
cheers , had to make sure first, had visions of blown meter or blown bits of car lol
Offline Profile Quote Post Goto Top
 
highlanderian
Part of things
[ *  * ]
Guys wee bit stuck again, just tried this got nowhere lol, my car doesn't seem to have a cat or an o2 sensor. My readings stayed at fifty from cold to past 80 degrees. Is it possible to use some other procedure on a car with no o2 sensor

ian
Offline Profile Quote Post Goto Top
 
highlanderian
Part of things
[ *  * ]
Anyone ? Lol
Offline Profile Quote Post Goto Top
 
JustbeCoz
Part of things
[ *  * ]
Just thought i'd resurrect this old topic as it has some good info about what has recently become a hot topic. For those without a catalyst/ o2 sensor the duty cycle or dwell reading should be a steady 50% as there is no closed loop control or feedback from the o2 sensor. A lot can be done with a bit of google and a cheap multimeter. So many cars used KE Jet that the principles and other info can be had from Porsche and VW forums and others.
Offline Profile Quote Post Goto Top
 
bing
Newbie
[ * ]
Hi there,

This and http://www.landiss.com/mixture.htm were great help with mixture adjustment!

However I found something quite weird with my car while trying to adjust the mixture

1)
According to http://www.landiss.com/mixture.htm, the static duty cycle should be 70%, which means the voltage between pin 2 and 3 on the X11 connector should average around 4v.
I'm averaging around 8v, which is around 33% duty cycle.

2)
The "full load contact" static test works for me, and it's correct. However the idle contact test (where you deflect the air flow plate to change the duty cycle) does not. moving the air flow plate makes no changes to the duty cycle with the engine off ignition on.

3)
According to the guide above, the car should enrichen when you rev it up (make sense), so at 2500rpm, the duty cycle should be higher than what it is at idle
With the engine warm and idling, my duty cycle is around 8v or 30% (rich). However when i rev the engine to 2500rpm, it drops down to 50%.
When I open up the throttle, i'm suppose to see momentary enrichment, the duty cycle should temporaily drop (voltage goes up), however it's doing the opposite.

4)
I tested the air flow meter with the ignition on and engine off, it is within the correct parameters, and the voltage increases/decreases smoothly as you move the plate.


So it would seem like the computer isn't getting the air flow meter readings, even though the meter itself is working... weird... Any thoughts?


Thanks!
Canadian 190e owner :)
Edited by bing, Sun Nov 18, 2012 2:27 am.
Offline Profile Quote Post Goto Top
 
1 user reading this topic (1 Guest and 0 Anonymous)
« Previous Topic · Engine · Next Topic »
Add Reply


Email me if anyone replys