Where is the x11 socket? Near battery? Can you give me clearer instruction regarding "duty cycle"? Have heard the term but not sure I follow you. Thank you for your input

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Dale

Usually it is close to the ignition control unit - on a left hand drive car this is usually on the driver's side of the car on the inner wheel arch.

Here's a picture of it on my W201 =>



(Ignore the screw drivers in this picture I was arsing about with something else)

There's a little cap that needs to be removed to see the plugs underneath.


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Before ECU's started having Obi Wan Kenobi ports that plug into handy little devices that tell you the error code, one way to measure a fault with the ECU was to measure Duty Cycle.

On a CIS (continuous injection system) W124 / W201 (and others) the way to do this if you have the same x11 diagnostic port as shown above is to measure the voltage between pins 2 and 3. You (should) get a constant varying voltage across these pins.

This is an output from the ECU that not only gives an error signal if there is something wrong but also an indication of the mixture richness.

Duty cycle is a percentage value that corresponds to the time the signal is "on" or "off". See for example =>

https://en.wikipedia.org/wiki/Duty_cycle

If you can borrow / buy / steal a multimeter that can measure frequency (so there's a Hz button) there's more often than not a Duty cycle function built in (% button). These are ideal instruments which will give you a handy value.

If you haven't got one of these instruments then the following article helps you do it a harder way =>

BOSCH KE3-JETRONIC MIXTURE ADJUSTMENT

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

I think Stretch will agree with me here, diagnosing CIS is one of the most fun things you will ever don on a car. My 190E 2.6 has been a bear lately and I'm not sure why. I adjusted the duty cycle once already, replaced the EHA, replaced the hall effect sensor, coil, distributor, rotor, plug wires, and plugs, replaced the fuel filter, and it started running poorly again a few weeks ago and tthrew a code for the oxygen sensor. I replaced that and everything seemed off again. The computer kept on throwing that same code so I replaced it, the MAS relay, and the EZL. I can't currently get the duty cycle to even read correctly at static idle, car smells strongly of gas, and I have found out the air flow meter potentiometer is bad as well as some of the vacuum hoses. I also just replaced the idle air control valve and adjusted that potentiometer as best I could and now the car isn't stalling but idling way high. This is why I am swapping in a 3.0l M103 and converting to Megasquirt.

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Current: 1975 450SEL, 83 300D, 88 Yugo GVX, 90 300D OM603 swap, 91 F150 4.6 4v swap, 93 190E Sportline LE 3.0L M104 swap, 93 190E Sportline LE Megasquirt, 03 Sprinter, 06 E500 4Matic wagon.

Well that sounds like standard CIS operating procedure: Replace everything and still get no where!

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For your problem it sounds like you're in the air flow potentiometer / mixture screw roll of death. I've figured out that on my KE system if you set the air flow potentiometer with the engine stopped and ignition on, to be about one tenth of the 0.7 V dc value then when the engine is running (and the air flow sensor plate has moved down slightly) you should be about at the right place.

This is a guesstimate value - I've got WIS information that says it should be at another value with engine stopped ignition on but that setting doesn't work for me.

Once you've got the air flow potentiometer set you should be able to set the mixture screw. A good trick is to remove all injector lines at fuel distributor (unscrew) - jump contacts on fuel pump relay plug (remove relay) and then adjust screw so the fuel flow coming out of the distributor has just stopped. Warning - press down on air flow plate and the fuel shoots out! This is the procedure in the FSM. On my car the screw needed to be turn way back - anticlockwise at least half a turn - for the engine to start. It was still too rich.

If all of the other new sensors are working correctly then you should be able to fine adjust the duty cycle to 50% on the adjustment screw.

Job done.

As easy as that!

(yeah right)

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Such a smooth running car at driving speed but not so much while idle. Not sure it's the best vehicle for my son and daughter to share as their means of transport. Retrospect says I should have gone with an Asian ! Point and shoot


Does it really matter HOW I sent this message?

__________________
Dale

Wouldn't be as much fun! But as reliable as these cars are, electronic fuel injection is much less temperamental

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Current: 1975 450SEL, 83 300D, 88 Yugo GVX, 90 300D OM603 swap, 91 F150 4.6 4v swap, 93 190E Sportline LE 3.0L M104 swap, 93 190E Sportline LE Megasquirt, 03 Sprinter, 06 E500 4Matic wagon.

Well I figure I should update this thread since I started it earlier this year and have some results from a couple added parts. I installed a new OVP relay as well as a new voltage regulator and these two items seemed to have taken care of a this rough idle and stalling issue as well as a rabid ABS light and an intermittent SRS light! Since making these changes, both dash panel lights no longer glow (knock-on-wood ) as they have been doing recently.

I know it's never a good idea to simply throw parts at it but from all the threads I read regarding these issues and the fact I wasn't sure if ever these items had been changed, it was worth the gamble. It seems to have paid off!

Now, on to replacing rear suspension links....

Dale

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Dale