w124 idle fault

[roofless]

over the last week my w124 e220t m11 engine has started to suffer from the idle fault in D & R when the idle drops & the car can stall ect this seems to be very common on 90s mb cars so had a go at it to find the idle speed stabilizer valve was dead when the car was running at idle speed so a quick check showed power at the plug on top of the valve so my next step was to remove the valve & take it apart & clean it then use silicone spray lubricant to free it all up .. gave it a go to find it pulse away as it should & two days on my car still idles even at all times :-D as far as i know unlike the old k-jet with a air bypass valve on the motronic system the idle speed valve takes a pulse from the ecu which is altered to compensate for load as the ecu is aware of the engine speed so if it drops it will alter the pulse to maintain the required idle speed..... .................................................................................................
[/LIST]

 

[television]

over the last week my w124 e220t m11 engine has started to suffer from the idle fault in D & R when the idle drops & the car can stall ect this seems to be very common on 90s mb cars so had a go at it to find the idle speed stabilizer valve was dead when the car was running at idle speed so a quick check showed power at the plug on top of the valve so my next step was to remove the valve & take it apart & clean it then use silicone spray lubricant to free it all up .. gave it a go to find it pulse away as it should & two days on my car still idles even at all times :-D as far as i know unlike the old k-jet with a air bypass valve on the motronic system the idle speed valve takes a pulse from the ecu which is altered to compensate for load as the ecu is aware of the engine speed so if it drops it will alter the pulse to maintain the required idle speed..... .................................................................................................
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Thats what I call a good post

 

[turnipsock]

Heck, I didn't know it was that simple. I've been driving around with my left foot on the brake and my right on the accelerator to keep the idling speed up when the car was cold.

All I have to now is find the idle speed stabiliser.

 

[roofless]

Heck, I didn't know it was that simple. I've been driving around with my left foot on the brake and my right on the accelerator to keep the idling speed up when the car was cold.

All I have to now is find the idle speed stabiliser.

if it's your 320 it's on the rhs from the front on the iner wing just follow the thick vac pipe from the trottle body to the valve on the iner wing it's easy to check with the car at idle put your hand on it & you will feel it pulse if not it's faulty

 

[roofless]

the motronic system is on page 59 on this link http://www.scribd.com/doc/3215544/Bosch-fuel-injection-systems

 

[kth286]

over the last week my w124 e220t m11 engine has started to suffer from the idle fault in D & R when the idle drops & the car can stall ect this seems to be very common on 90s mb cars so had a go at it to find the idle speed stabilizer valve was dead when the car was running at idle speed so a quick check showed power at the plug on top of the valve so my next step was to remove the valve & take it apart & clean it then use silicone spray lubricant to free it all up .. gave it a go to find it pulse away as it should & two days on my car still idles even at all times :-D as far as i know unlike the old k-jet with a air bypass valve on the motronic system the idle speed valve takes a pulse from the ecu which is altered to compensate for load as the ecu is aware of the engine speed so if it drops it will alter the pulse to maintain the required idle speed..... .................................................................................................
[/LIST] View attachment 6861 View attachment 6863

That is actually part of the 'fuel evaporation control system' and is the Regeneration Switchover Valve.

The engine sucks the fumes from the petrol tank via the charcoal filter in the wing via this purge valve and burns the fumes.

The valve is pulsed by the main engine computer (ECU) once certain criteria are present ie.

* coolant temp above 70

* engine started at least 2 minutes

* engine not in deceleration mode.

Well done for getting it working as they cost over £100.

 

[television]

That is actually part of the 'fuel evaporation control system' and is the Regeneration Switchover Valve.

The engine sucks the fumes from the petrol tank via the charcoal filter in the wing via this purge valve and burns the fumes.

The valve is pulsed by the main engine computer (ECU) once certain criteria are present ie.

* coolant temp above 70


* engine started at least 2 minutes

* engine not in deceleration mode.

Well done for getting it working as they cost over £100.

David, stumpy has posted asking for info on this this morning, any chance that you could answer his post

 

[stumpy]

David, stumpy has posted asking for info on this this morning, any chance that you could answer his post

Thanks TV - I have removed the rubber connector from the resonator to take to MB and get a new one. It has a plastic insert in the open end with a filter across it. No idea what it does.

 

[roofless]

That is actually part of the 'fuel evaporation control system' and is the Regeneration Switchover Valve.

The engine sucks the fumes from the petrol tank via the charcoal filter in the wing via this purge valve and burns the fumes.

The valve is pulsed by the main engine computer (ECU) once certain criteria are present ie.

* coolant temp above 70

* engine started at least 2 minutes

* engine not in deceleration mode.

Well done for getting it working as they cost over £100.

yes i am happy to have saved a few bob & was aware that mb call it a regeneration valve but it is baseicly what bosch call the idle stableizer & a large part of it's job is to work via the ecu to control the idle speed under load by adjusting the airflow when at normal temp this is why when it's faulty it's not to bad in N or P but the car dies when in D or R it's a bit like chips & french fries but as i am using the bosch manual i used french fries..see P59 http://www.scribd.com/doc/3215544/Bosch-fuel-injection-systems

 

[roadhog]

Aren't they known as Freedom Fries now?

Good fix on your idle problem. I like nil cost fixes.

 

[kth286]

yes i am happy to have saved a few bob & was aware that mb call it a regeneration valve but it is baseicly what bosch call the idle stableizer & a large part of it's job is to work via the ecu to control the idle speed under load by adjusting the airflow when at normal temp this is why when it's faulty it's not to bad in N or P but the car dies when in D or R it's a bit like chips & french fries but as i am using the bosch manual i used french fries..see P59 http://www.scribd.com/doc/3215544/Bosch-fuel-injection-systems

roofless

that is wrong - you have an all electronic engine control, and there is no mechanical device for controlling idle. It is all done electronically with the ECU advancing or retarding the spark to control idle according to engine load/temp etc etc.

That switchover regeneration valve being gummed up was probably stuck in the open position. That means constant engine vacuum at low idle revs was continually sucking fumes from the petrol into the engine and causing the engine to stall. A working regeneration valve, pulsed by the ECU at the correct moments, would prevent it being open at an inopropriate time, and thus the engine would have been prevented from stalling.

 

[roofless]

roofless

that is wrong - you have an all electronic engine control, and there is no mechanical device for controlling idle. It is all done electronically with the ECU advancing or retarding the spark to control idle according to engine load/temp etc etc.

That switchover regeneration valve being gummed up was probably stuck in the open position. That means constant engine vacuum at low idle revs was continually sucking fumes from the petrol into the engine and causing the engine to stall. A working regeneration valve, pulsed by the ECU at the correct moments, would prevent it being open at an inopropriate time, and thus the engine would have been prevented from stalling.

yes i have just edited my reply to this post as you are right my reading the book on this has drawn me away from the mercedes own way of using the motronic system when i was reading the theory but at the end of the day it worked for me & thank for your input & keeping me right

 

[Number_Cruncher]

>>there is no mechanical device for controlling idle.

Is that true?

While using ignition advance for idle speed control does provide some fine and fast control action, it is quite limited, and usually, there would be some mechanical actuation.

Is this a drive by wire car?, where the throttle valve is driven by an electric motor? If so, this will also be used by the ECU in conjunction with ignition advance to provide idle speed control.

 

[television]

>>there is no mechanical device for controlling idle.

Is that true?
.

Yes cars fitted with the rotary air valve do not have an idle adjustment screw, and this started back in the mid 80s on KE, and not seen since.

 

[Number_Cruncher]

>>Yes cars fitted with the rotary air valve do not have an idle adjustment screw

Sorry, I think we're getting our wires crossed Malcolm - yes, I agree, if there's a rotary idle actuator, there's no idle adjustment screw.

What I was asking about was this;

>>there is no mechanical device for controlling idle.

By which I took this phrase to mean no auxilliary air valve, no rotary idle actuator, no drive by wire throttle plate no moving parts controlling the idle speed are fitted, and the only idle speed adjustment mechanism being via the variation of the ignition timing.

Which is why I questioned it, there's usually some mechanical means of compensating the slowly varying levels of engine friction and mechanical loss between hot and cold conditions, while individual cylinder ignition timing adjustments can result in a smoothing of idle quality which happens much faster - a higher bandwidth adjustment, but with limited range.

 

[roofless]

just to clear up a few things my car is not a fly by wire but at the same time other than cable adjustment for tension it is not adjustable due to the throttle must rest on the stop to make contact with the micro switch in the idle position at this point the ecu controls the idle via the motronic valve ect. when on cold start then when it warms up to normal temp the regeneration valve also controled by the ecu helps to mantain the required idle by restricting the vachumm to the throttle body as required this is when my fault ocurred by sticking open as kth286 has said to give excess unmeterd air in at the wrong time...now this is the part i get stuck on is the motronic valve opening the throttle slightly at idle when warm & adjusting the air flow to cope with load to allow the required idle or is the ecu using the regeneration valve in conjunction with the fuel & spark to maintain the idle when at normal temp. the reason i ask is the ecu could just close the valve at idle at normal temp like it does when on warm up but it still opens & closes as required so it in a way is it a aid to the stability of the idle

 

[television]

Surely nothing moves other than fuel enrichment when cold, you can ignore the throttle body switch on Motronic, it purely tells the Main ECU that the engine is at idle, failure of this switch, and the idle goes up the 1200 fail safe speed.

The sensors play a big part in this system, and it is these sensors that tell the ECU what to do with the fuel