W124 2.0l KE Jetronic aux air valve

kdavies3

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Hi all, I'm new here so please be gentle with me.:D
I am working on a friends 190 2.0l manual with KE Jetronic.
The symptoms are that the car will start and idle but at low speed.
The engine will not rev without spluttering and coughing, as soon as the engine warms up it seems fine.
I've checked the auxiliary air valve and found that it is closed all the time cold or hot. I can move the blade with a screw driver and I've cleaned it, I get very little resistance across the electric terminals on the valve and also if I apply 12v across it nothing moves surely it should open?
I'm suspecting the the valve is knackered, can anyone point me in the direction of a new or replacement one, also can anyone confirm my diagnosis?

Thanks in advance for any advice.

Cheers
Kev, South Wales.
 

television

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Welcome to the forum:D

The resistance of the aux air valve is 40Ω.

You have the thermo time switch terminal G and W =93Ω below 15c G and earth 93Ω.

Do not forget the cold start valve
 

wireman

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It may be ok, the valve closes when warm and only opens when its quite cold. It serves to raise the tickover speed on cold starting.

However here's my bit about it:-

I have not dealt with a merc aux air valve but in the past I have dealt with similar types on vauhall and vw units (LE jetronic), both had sticky deposits inside the valve which did not allow it to open when cold with the same symptoms you describe.

The valve has a steel plate which passes over an orifice to cut of aux air when the engine is warm, the plate rotates about a pivot and is controlled by a bi metalic strip which is heated both by an electrical heater wound around the bimetalic strip and conduction of engine heat from the mounting bracket. In service the innards get a coating of goo/varnish which limits the valves ability to work correctly.

I have succesuly opened and cleaned these valves to restore normal function by cutting (carefully fileing) back the rolled over egde of the larger diameter flange so that the case can be split into it's two die cast halves, the plate can then be removed for cleaning making sure that on reassembly the plate engages the bimetalic strip.
Reassemble the valve with an epoxy adhesive to hold the end cover in place.
 
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kdavies3

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Hi Malcolm and thanks for the welcome. :)

Can you tell me where the thermo time switch is?
Is it the sensor at the front of the head with 3 terminals one of which operates the temp gauge? If so are the other 2 terminals the thermo time switch?

cheers
Kev.
 

television

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Just behind the thermostat on the top of the block
 

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It may be ok, the valve closes when warm and only opens when its quite cold. It serves to raise the tickover speed on cold starting.

However here's my bit about it:-

I have not dealt with a merc aux air valve but in the past I have dealt with similar types on vauhall and vw units (LE jetronic), both had sticky deposits inside the valve which did not allow it to open when cold with the same symptoms you describe.

The valve has a steel plate which passes over an orifice to cut of aux air when the engine is warm, the plate rotates about a pivot and is controlled by a bi metalic strip which is heated both by an electrical heater wound around the bimetalic strip and conduction of engine heat from the mounting bracket. In service the innards get a coating of goo/varnish which limits the valves ability to work correctly.

I have succesuly opened and cleaned these valves to restore normal function by cutting (carefully fileing) back the rolled over egde of the larger diameter flange so that the case can be split into it's two die cast halves, the plate can then be removed for cleaning making sure that on reassembly the plate engages the bimetalic strip.
Reassemble the valve with an epoxy adhesive to hold the end cover in place.

Thank you for that description of how it works
 

Alex Crow

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don't think this one has thermotime switch. the aux air valve is permanent live and the cold start jet is via the ecu. from memory.
 
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kdavies3

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Thanks all,
I have stripped the Aux air valve as per Wireman's instructions (thanks for that).
Unfotunately whilst the mechanism is not stuck it appears that the bi-metal strip is defunct, even though it gives a resistance of 42 ohms.
As for the Thermo time switch I get open circuit between the terminals and from each terminal to earth.
That said does that not only provide a feed to the cold start valve during cranking?
As I said the car starts fine just doesn't want to rev until its warmed up.
Anyone have any suggestions as to where to find a replacement aux air device?

cheers all. :D
Kev.
 

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Should be some around at breakers
 

Number_Cruncher

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>>just doesn't want to rev until its warmed up.

Where does the KE jetronic gets its power supply from on 190s?
 

Number_Cruncher

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I was thinking more along the lines of the possibility of OVP problems.
 

television

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I was thinking more along the lines of the possibility of OVP problems.

The engine ECU were not protected until around 1992 / 3 and on.

Yes the OVP relay can affect the later cars on idle,,dont think is was ever on the 201
 

Number_Cruncher

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>>dont think is was ever on the 201

I haven't worked on many 190s, but, I have replaced one OVP which was showing similar symptoms plus the usual ABS light on. So, some 190s definitely had OVPs.
 

Alex Crow

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your three pin device is a combined temp sensor for the gague, and fan switch for the cooling fan. if you short the two terminals to each other with ign on you will hear the clutch 'clunk'.
 

Alex Crow

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the ke-jetronic is supplied by an ovp on every model of every year. just very difficult to find on a 190! (right against the bulkhead to the o/s of the battery)
 


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