hey Alex

I am in the same boat, after trying new potoentiometer and experimenting with mitures with the EHA on/off, I would also like to know what the factory specs should be, one morning after messing with the mixture I couldn't get it started either, I needed to get a visual of my buddies 16v flow plate to get it to start agian,, and I just can't find the spot where it was originally at.
thanks

Alex,

I hope that ticking noise wasn't a valve kissing a piston??? If it didn't idle right after you corrected the intake cam, I would recommend a compression or leakdown test. You need to check if you damaged anything.

If you nicked or bent a valve you can forget about it idling right. It will run fine off idle, but it won't want to idle.

Dave,

The factory specifies a 0 EHA ma reading and 50% duty cycle reading. A negative ma reading from the EHA represents a rich running condition and a positive means lean. As you lean and richen the duty cycle will jump around. Stevebfl recommends a slightly rich reading (mid 40's duty cycle) for best performance.
My reading for some reason are the exact inverse of what they should be. Go figure. BTW I believe my pot (wow man I'm so stoned) is bad but I have managed to mask its behavior by disconnecting the throttle position sensor. But that's a whole nother topic.

Tinker

Hey Tinker,

I hope so too, but let me ask you this, can a valve still kissing the piston even the Valve clearance was in spec????

I did not do a pre-compression test before I changed out the timing chain so I didn't know what they were. However, post timing chain replacement, the number two cylinder is low only 100psi while the rest are in 165-170psi. Is this why it won't hold idle at all? it runs real good, smooth accellaration, it hasn't been this good in a while, except for the idling.

As you know right now the car is dead in my driveway and so does Davect. I have never done this part of adjusting the duty cycle on this car, I need some test points and what plug and so on. Though, I'm not a stranger to sinewaves and duty cycles from work, we have lots of robots that used Gallil stepper motor control with encoder signal amplifier.

How do I get back to nominal position and that is my problem right now. I hate to bring it to the dealer and before you know it, they'll tell me I need a whole new mass flow sensor this will be ouch chihoahoa!!!!

Hey Dave! Good luck with your car and please let us know how you will make out. Let me know if you want to go boating on Candlewood lake sometime this Summer.

Alex

Alex,

It doesn't matter if the valve clearance was correct. The relationship of the valve timing to the piston was altered when you misadjusted the intake cam.

Pressure test the cylinder and post results.

Tinker

Hey Tinker,


Never done a leak down or pressure down test before. I don't even know what it needs to perform this test. I did a compression test and as I stated before that cylinder number two is low and out of spec.

I'm in the middle of moving, and you know it is very hectic. I can't spend too much time on this car, I need to pack the kids and wife, buy a house, and sell a house, and lots of other fun stuff.

I order a new Bosch potentiometer for the air mass sensor and will give it a shot before I have it tow to the dealer. Any one have some advice for what nominal resistance for me to set before I install the pot???

Thank you
Alex

Alex,

you can't get the 16v to start at all???, did you turn the mixture screw too many times, or have the pot off?
I have been messin with the pot on the 16v , and also srcewing with the mixture, I finally droped the dime and got the hugh MB service manual, It make it alot easier to figure things out,
Engine 102.983(86 16v ...(87 might be differnt theres a whole differnt section for it)) testing A/F sensor,accel enrichment,
multimeter on mA, 20degC
discontect O2, start engine, test EHA nominal value 5-15mA Increase engine speed quickly ,current should increase,,, if so.. end of test, lol
if not stop engine
airflow plate must be deflected see if it has pressure before lower edge of the cylindrical part off the air funnel, if not adjust mixture screw/or bad distributer
testing the pot terminal 3 and 1: approx 5v
terminal 2 and 1 :0.2-0.5v if ok
slowly defect plate ,voltage should increase continously to 5 volts
if not replace the A/F unit.

I found my first start stalls seems to be the NEW coolant temp sensor, I installed last summer, manual states +20C =2.2-2.8kohm (mine 3.1k)
0C=5.5-6.1k ohm(mine 6.2) everything else checks out to the book.
Hope this helps

Dave

Hi Dave,

My car is an 86. At the moment it doesn't want to start at all whatsoever. Yes, indeed I turned the mixture screw too many time. The Mixture screw feels very weird now, what I mean is when I depress the screw and when turn I don't feel it is engaged any more, it feels like I had broken a gear or something.

I like the procedure you wrote very nice and short, except that I don't know the test points to measure the EHA reading. I understand that the meter has to be in mA, but where are the test points, could you please write these test points down for me.
And also when you say deflect the plate do you mean press down on the throttle flappy thing?? Sorry to ask dumb questions but I have to make sure.

Please response if you can. So, did you get your car back on the road yet? Thank you and I'll talk to you soon.
Alex

alex the Eha test point is on the fuel distributor, black box 2x3in
with two wires , pull it off and put it back on 3/4 of the way so you can get the meter pins on it,
follow the pot wire ,it has a harrness a few iches away follow the wires, and pry off the top cap, and leave it hooked up so you can measure it from above it,
the the throttle plate has to have pressure on it before it moves past the bottom of the tube, or it will NEVER start, if you can not feel pressure when turn the mixture screw it is broke you need a whole new A/F sensor or at least a new mixture screw. I have a a/f sensor if you need it.

Ya my 16v was down one morning when I was playing around with the mixture screw and running around the block to see differnt driving styles, I lost count of turns forward and back and the plate was out of wack. luckly I got to check out my buddys to feel where the pressure was on the airflow plate and turned the mixture screw to the point and it fired right up, I decided to get the manuals before a new a/f sensor and it seems to be within spec, I need to go and get duty reader from sears this week there is a hugh section on duty.

Thanks Dave,

I'm glad to hear that you 've got your car running again. I think, I 'm going to Sear to get me a duty cycle reader also.

That's great that you have a whole A/F ass'y. But my problem right now I may just need the mixture screw only, I read in one of the thread that dealer do carry this item. I want to take the mixture screw ass'y out to take a look but it doesn't seem that simple. Do I have to take the whole top of the A/F ass'y off to gain access to the screw underneath?? Man! nothing is easy on this car....

Where do you get your 16V manual? I think I need one badly.

Once again Dave, thank you for all your help, I may contact you for your A/F. Have a nice day.
Alex

hey Alex

The mixture screw is like 10 bucks at carriage house NL, but I bet Phil at mercedesshop will get it to you cheaper, I know you will have to die-grind the mixture rivets out and Im not sure how the new one bolts up? make sure there is no leaks,
I got the my manuals off of ebay used for 120, for the engine
102 and chassis,(stacked on top of each other is 6-7 inchs of reading) they have extra chapters just for the differnet
16v's , Ask the dealer for the shop book thay have them there

hope this helps
Dave

Alex,

Why don't you humor me and run a compression test and see if the numbers are the same as before? If they are and it ran before you fiddled with the mixture screw, then you can look to other sources for your problem(s).

Be aware that there is probably less than 1/3 of a turn on that mixture screw between way too lean and way too rich.

Tinker

Thanks for the info there Dave. I'm hoping that all I need is the mixture screw not the whole A/F ass'y. I haven't gotten around to work on my car lately. I will go to the dealer to get me a mixture screw tomorrow.

Tinker, I did not do a compression test before the timing chain replacement. After timing chain replaced, the engine ran but I heard some tickings noise that I didn't like. I then opened up the valve cover and checked the cam shafts position against the crank shaft and this was how I found out that the intake cam shaft was off by a gear tooth. I corrected the intake cam shaft, took it for a test drive, she ran beautifully except for the idle, it stalled out at idle all the time. This was when I decided to mess with the mixture screw, I screwd it up royally, it can't even start it up, I also did broke something in there, I can no longer have any resistance when I move the screw.

Have you ever replaced this mixture screw? do I have to take the whole A/F off or I can just replace it by itself?

I did do a compression test and here is the order 1= 160psi; 2=110psi; 3=165psi; 4=165psi.

Cylinder number 2 is low but for a 200k miles maybe this is expected?

I don't expected to take the head out soon, I just want to get this car start and hold idle, I'm the middle of moving so the car's priority gets low right now.

Thank you for any help.
Alex

Hey Alex,

that # two cylinder doesn't sound so good at 110
the pressures should be 145-175psi with no more 15%
differance between the cylinders,

it is time either get a leak down tester, you will need
the special tool about 70-100 bucks, and a compressor, to pressurize the cylinder and measure the leakage, and you can listen to hear where the leaks is( exhaust,intake,oil tubes)
or just take the head off ,and hope there is just a burnt valve

here is a great thread from another CT16v from last year about fixing the head
190E 2.3-16 Is Sick! Need Help!!

hope this helps and good luck
please keep us posted Alex

Hi Dave,

Sorry to get back so late, but here is my situation. I'm in the middle of a move out state. I don't have the time right now to do any heavy duty work. I understand that the cylinder number two is not so hot, but from the test drive before I messed up the idle was not so bad that I can deal with it. I will deal with the head once I'm settled to the new place.

I just got a new potentiometer and a new mixture screw. Oh! by the way nothing was harmful neither the A/F or screw, I adjusted so much that it ran out of adjustment, but I'm going to replace the screw any way.

I did use a drill and some easy out tools, I was able to remove the mixture screws today.

Now my questions are where should I put my plate in the funel using the mixture screw??? Should I put it close to the bottom ring, top ring or a 1/16" below the bottom ring??? I have no idea now??? Should I with the key on adjust the mixture screw and monitor some test point for 0.7V?? I forget what test points I should monitor, while adjusting this mixture screw. I also confuse with the EHA test point.

Let me re-iterate this one more time. 1/ How do I adjust the EHA and 2/ How do I adjust the ON/OFF cycle, 3/ How do I adjust the 0.7V. If you can step by step for me on this I would be so damm happy and would kiss a camel any day.

Or to make it less confusion, what I have is a new mixture screw, a new potentiometer, and an unknown plate position. What would you suggest that I should do to head in the right direction.

As always, I owed this site lots of favors.

Alex

Here we go again, got the A/F back on with new pot and new mixture screw. Took Davect advice adjust the mixture screw so the plate has pressure right away as soon as you try to deflect it. I actually put it about a 1/16 of an inch lower, this seems to start better.

The car is running good now and doesn't have any hesitation. However, the idle still bad, can not hold idle at all, if I let go the gas pedal engine will stall.

To temporary solve the idle issue, I had to use the throttle stop screw to increase the rpm to about 1700 RPM at idle, it's embarassing at the stop light, sometimes it goes up to 2500 RPM.
Could this be an idle control valve? how about the magnetic sensor above the crank pulley? how critical is its position, I had to replace this sensor during the timing cover removal.

It is running but sure is not like a mercedes at idle though. Thank you for any advice.

Alex