M104 regeneration valve

[evo-number-one]

I have started to experience a problem with my 1994 E280 Estate (approx 90,000 miles) which I hope someone can kindly throw some light upon.

When starting the car from cold, the car settles and ticks over around 650/700rpm - possibly a little low - but still nice and smooth. As the car warms the regeneration valve pulses away. The car pulls and operates perfectly at all speeds.

Once the car is completely warm (reading just over 80 on the temp gauge) the car still pulls as it should, but seems to be not quite as smoothly and when finally slowing to approach a junction or at a standstill, the tick-over is now down in revs as if its about to stall (although it never does). Coinciding with this the regeneration valve no longer pulses. Should this continuously pulse?

When the regeneration valve is not pulsing, the tick-over speed never hunts, it just stays low - almost as if it is going to stall. Initially, I replaced the regeneration valve believing it to be faulty, but the new one has made no difference.

At all times, the car runs on 6 cylinders and is not misfiring (in the past I have experienced those symptoms with coil and harness problems – both of which have been sorted – and the current problems in no way have the feel or restrictions that I experienced with those issues).

Could somebody please describe how the regeneration valve works within the emission/evaporation system and explain to me what series of events cause it to pulse. If the charcoal filter (which although I have a stamped service book, I do not have any invoice/written evidence has been changed) is blocked and no longer efficient would this cause the valve to not operate?

Maybe I am going up the wrong path with the valve/filter - but the car runs perfectly when its pulsing.

If somebody else has experienced the above and cured this issue I would greatly appreciate some guidance as to the cure.

Regards

Bob

 

[star]

Try cleaning the throtle venturi 1st.

 

[evo-number-one]

Star, thanks for quick response.

If by the venturi you mean the throttle body butterfly valve, I had already tried that before I started looking at the regeneration valve (apologies for not mentioning that in the original post).

There was not much visual dirt/gunk but cleaned it thoroughly anyway, resulting in no change.

I also previously tried some fuel addative/cleaner - again no change.

The fact that I now notice that everytime the problem arises the regeneration valve is not pulsing (and whenever the car runs spot on it is pulsing) is what has lead me down the regen' valve route, but not sure if pulsing/non-pulsing is a red herring.

Bob

 

[star]

try and block the pipe to manifold to see if that improves, the valve can sometimes stick.

 

[mr rosher]

I have started to experience a problem with my 1994 E280 Estate (approx 90,000 miles) which I hope someone can kindly throw some light upon.

When starting the car from cold, the car settles and ticks over around 650/700rpm - possibly a little low - but still nice and smooth. As the car warms the regeneration valve pulses away. The car pulls and operates perfectly at all speeds.

Once the car is completely warm (reading just over 80 on the temp gauge) the car still pulls as it should, but seems to be not quite as smoothly and when finally slowing to approach a junction or at a standstill, the tick-over is now down in revs as if its about to stall (although it never does). Coinciding with this the regeneration valve no longer pulses. Should this continuously pulse?

When the regeneration valve is not pulsing, the tick-over speed never hunts, it just stays low - almost as if it is going to stall. Initially, I replaced the regeneration valve believing it to be faulty, but the new one has made no difference.

At all times, the car runs on 6 cylinders and is not misfiring (in the past I have experienced those symptoms with coil and harness problems – both of which have been sorted – and the current problems in no way have the feel or restrictions that I experienced with those issues).

Could somebody please describe how the regeneration valve works within the emission/evaporation system and explain to me what series of events cause it to pulse. If the charcoal filter (which although I have a stamped service book, I do not have any invoice/written evidence has been changed) is blocked and no longer efficient would this cause the valve to not operate?

Maybe I am going up the wrong path with the valve/filter - but the car runs perfectly when its pulsing.

If somebody else has experienced the above and cured this issue I would greatly appreciate some guidance as to the cure.

Regards

Bob

hi bob, i don;t know if this is any help to you, i have the same problem with my e280 1993, in the last 8-9 months i have changed everything i can think of, you may have read my post, last week i diconnected the air mass plug and she was fine, now i have been getting air mass code readings on the blink tester even though this was new about 7 months ago and she had only done about 1000 miles since, so bought a new one a bosch, fitted it, and the code went, after two miles same thing just died at a roundabout, rechecked the codes, and air mass again, i since found that after five minutes of running the o v p r gets warm and this is linked to the air mass, within the last two days she's now doing 10 miles to gal instead of 30 - 32, so iv'e ordered one but they say it may take a week or so, the thing im worried about has the o v p r done in the air mass again ?, i will keep you posted when i get the new o v p r.

rod

 

[evo-number-one]

Thanks Rod.

Yes, I was looking at some of your posts earlier today - must be infuriating after all the time, effort and work that you yourself have carried out.

I was trying to get an understanding of how and what triggers the regen valve and when exactly it should be pulsing, because when the problem arises (and this only when the car has warmed up), the regen valve is not pulsing. If the car is warm and teh siad valve is - then no problems.

When the problem does arise, the car has never actually died on me -only idles badly- but I will have a play with the afm plug and will also look out for your update re the OVPR.

regards


Bob

 

[kth286]

evo

valve works from pulses supplied via main engine ECU; PROVIDED :

1. coolant temp over 70 C

2. more than 2 minutes after starting engine

3. engine not in deceleration mode.

If there is any doubt, change charcoal filter in wing as it should be every 70K miles approx.

As STAR suggests, remove vacuum line from purge valve to inlet manifold for a while.

Ensure the exposed end of line is airtight and then drive car to see if there is any difference. This will have eliminated the emission system from the equation.

You do say thet unit starts pulsing as engine warms up - which sounds wrong - unless the coolant temp sensor is going out of spec.

Coolant temp sensor may be your problem.

HOWEVER, you should be getting the codes read first, and go from there.

Is SX Sussex ? or anywhere near me.

 

[evo-number-one]

David

Many thanks for your post.

I'm in Ingatestone in Essex (SX), so unfortunately a little way from your goodself.

I will try and get the codes read, but currently not getting a chance during the week to get the car into a garage.

Meantime I will definately explore your and STARs suggestions re the vacuum lines/charcoal filter/temp sensor, along with Rods thoughts on the MAF/OVPR.

Much appreciated


Bob

 

[evo-number-one]

Been reading some of the other probs that fellow W124 E280 owners are posting up.

Over the past few weeks the issue appeared to become much less frequent, but I have still pursued a few things including getting hold of a blink tester.

Just as well, because end of the week the problem reared its head again and it appears to be more frequent than ever.

Just to recap, the problem is that the car occassionally idles quite roughly. It never hunts up and down, nor stalls - it just ticks over at 550/600 rpm. It sounds and feels quite lumpy, but more as if its out of tune or fuel related than its not running on all 6 like I experienced when I had the loom prob.

More often than not, if I pull upto a junction and it happens, when I pull away it seems fine and at the next juntion it ticks over low, but is not rough/lumpy. Last couple of days though the probs been been pretty constant whenever at idle.

Now, armed with my blink tester I am recording just the one error - code 17 on pin 8, which I believe is injector / cylinder 4.

Has anyone had experience of this code and can point me in the next (right) direction?

Appreciate anyones input on this.

Thanks

 

[Bolide]

Lumpy idle seems to be a common E280 complaint. You'd think that with the number of people trying to cure it we could come up with a fix

Perhaps part of the problem is that we have an effect but don't know the cause. In other words, no diagnosis because the cause of the illness isn't known

What can cause a misfire? I'd have thought it's only spark (lack of, wrong timing) or fuel (lack of, wrong timing). I can't see that the car can be starved of air

It'd be interesting to see the ignition traces on a diagnostic machine along with the injector pulse timing & width. What machine can do that?

I wonder if anyone has a plug-in telemetry unit that can store a few minutes of the relevant waveforms? If you stored the temp sensor data, battery voltage (from OVP?), AFM reading, TPS, CPS, revs, injector pulse data, ignition data & road speed and kept a couple of minutes in a buffer you could hit record after it misfires and store the data. Plot it against time and you should be able to see the cause & effect

Nick Froome
www.w124.co.uk

 

[evo-number-one]

The Loom of Doom strikes again......

Update:

A week ago with the problem becoming more frequent, I managed to get to read the codes and was presented with 17 on PIN 8 - Injector/cylinder 4.

Today, my local garage (who service the car) put the loom to the knife today and found not a lot........ left!!!

So, they have taken out all of the bad wiring (and beyond) and replaced with new and the car at last again runs exactly as she should.



Obviously only got her back this evening, but they appear to have done a great job - the rapidly approaching Family trip to Cornwall will be the test - but I am going to treat this as a definite temporary measure and get the loom replaced in its entirety - but for now their work relieves any immediate stress and I can budget for it being done properly at service time. With less than 90k on the clock, my plans are to keep this car for the long term, so this will be sorted.

Just one quick question - has anyone any experience or have heard of the MB replacement looms playing up? - This is to gauge whether to go original replacement or get the auto electrician to replicate. Obviously paying for an experts time is not going to be cheap, but quite feasibly cheaper than the £568 plus vat that MB want for the original part.

I would post up a photo of the state of the wiring that was removed and replaced, but its x-rated stuff and there maybe readers out there that are
squeamish and easily shocked.

Thanks for everyone’s help and advice from the forum on this.

 

[124coupe]

Hi, the insulation in the replacements (from MB) is not the experimental junk used the first time around - never heard of a second failure.

You can & should get at least 10% off the list price for the MB part - ring around until you do.

Straightforward job except for the wires to the knock sensors - tricky to reach....I have seen two cases where one was left hanging/tucked away - the result is poor acceleration as the ECU limits ignition advance.

 

[evo-number-one]

Many thanks - especially the tip re phoning around for a discount - 10% on this item would be more than welcome

Thanks again

E-N-O