Adjusting KE Jetronic via the diagnostic socket.

[The Crooner]

Following on from another thread, I think I am experiencing exactly what Star described - the CO2 is correct at the exhaust, but the engine is running rich as evidenced by sooty plugs.

Apparently one can adjust the CO2 by using a multimeter on the diagnostic socket.

Would anyone be so kind as to describe this process, or is it an arcane art reserved for the cognoscenti for which us mere mortals must pay?

Thanks

Tony

 

[television]

There are 2 methods, you measure upstream for controlled CATs and at the Exhaust no non controlled. You also need to know what ignition system is on the car and engine management as all things changed after 09-89

 

[124coupe]

As Malcolm says, process varies by engine type and emissions gear.

(with O2 sensor using pin3/duty cycle and a model-specific process and without O2 sensor using CO meter in the exhaust)

What is the engine you are trying to adjust? (M1xx.xxx)

 

[The Crooner]

Hi

102.982

 

[124coupe]

M102 with KAT (M103 KAT process is different – see below).

(Engines without KAT adjusted using CO meter in exhaust).

Firstly, and most importantly, you need to be sure as you can be that there is nothing broken, dirty or leaking causing your mixture issue.....assuming that, go ahead and test (with engine hot).

To do this the official way, you need a scope or a meter that measures duty cycle - i.e. the output you will measure is part of the time at earth potential and part of the time at effective battery potential - the duty cycle is the % of time the output voltage is AT zero.

I will assume you have a standard multimeter without duty cycle so a variation is needed to work out what average voltage reading represents the target duty cycle.

Find your X11 round diag socket.

Pin 2 is ground (black wire from meter goes here)
Pin 6 in at effective battery voltage - measure voltage here with engine running to determine your max volts figure (this will be lower than battery voltage because of circuit losses).

You now have a reference for 0V and the max volts figure (yyV) that the desired reading fluctutates to on YOUR car (taking into account battery condition etc etc).

So, 0V represents 100% duty cycle and yyV represents 0% duty cycle.

Target duty cycle for M102 with KAT is 50% + or – 10%.

40% voltage value = yyV x 0.6
50% voltage value = yyV x 0.5
60% voltage value = yyV x 0.4
Etc
(because 100% duty cycle is 100% of the time at 0V…)

Connect meter to pin 2 (black) and pin 3 (red) to measure your "duty cycle voltage".

The meter reading will fluctuate (if it doesn't then your O2 sensor is dead or disconnected or your mixture is so screwed the mixture adaption is at max). You need to estimate the voltage in the middle of the fluctuating reading and see where you are as a duty cycle value.

You will have an anti-tamper plastic plug over the adjustment hole which needs to be prised out (and kept to be re-installed).

3mm allen key is needed and you will feel it engage. You then press down gently until the adjuster makes contact (too hard and the engine will stall).

Record the current position (in case you need to back out your changes!) and then make small (1/8th turn) adjustments.

Anticlockwise is weaker mixture (corresponding to a lower pin3 voltage and a higher duty cycle) – fix this in your mind as you adjust!

Each adjustment will need 10 secs or so to stabilize before taking the reading.

(DON’T be tempted to rev the engine with the allen key engaged in the adjuster, let the adjuster spring up first.)


M103 KAT

Two differences:

Find and plug vac pipe from purge valve (on n/s wing) before taking readings.

Measure duty cycle at 2,500 rpm and record. Idle duty cycle to be + or – the value at 2,500 rpm.

 

[The Crooner]

Thank you.

We will see what we can achieve on an exploratory basis later in the week.

It all depends on the meter being up to the job.

Thanks again

Tony

 

[124coupe]

Thank you.

We will see what we can achieve on an exploratory basis later in the week.

It all depends on the meter being up to the job.

Thanks again

Tony

you only need a standard multimeter for the voltage method above.....if you want a duty cycle meter, Maplin do a good one for £19.95.

 

[s and k autos]

you only need a standard multimeter for the voltage method above.....if you want a duty cycle meter, Maplin do a good one for £19.95.

have you changed the coolent sensor

 

[The Crooner]

you only need a standard multimeter for the voltage method above.....if you want a duty cycle meter, Maplin do a good one for £19.95.

OK thanks, we'll try with what we have first.

Tony

 

[The Crooner]

have you changed the coolent sensor

Thanks, yes I have, and yes it was not working correctly.

Tony

 

[The Crooner]

Thanks to everyone for your help.

We tried to set the co2 as per the instructions but were getting inconclusive readings.

We did however find and fix a split in the vacuum pipe which goes to the charcoal cannister.

I took the car yesterday to the local performance centre:

http://www.corten-miller.co.uk/

Highly recommended, myself and family have used them for years.

They welded a boss and plug into the exhaust prior to the lambda sensor and set up the stage one setting by using the EGA.

They then fine tuned after the lambda.

Is running perfectly - no hunting and very responsive.

Amazing how even the gear changes are smoother.

Final job engine wise is to change the charcoal cannister and some pipework around it, then I'm going to pester you about suspension front and rear, and my sunroof, and do some remedial bodywork.

 

[124coupe]

Glad its sorted - not surprised you couldn't get the tuning right with an air leak....