230k lack of power - recirculating air flap?

[jamesmc]

After a couple of years of ownership I'm well down the DIY route of eliminating various issues (generally age related) on my 1999 CLK230K Cab.

One of those was the Oil soaked MAF issue. So I swapped out the MAF after replacing the blocked lower part engine breather system (fitted under the inlet manifold). That was a successful operation.. no oil reaching the MAF now.

Also changed out gradually over the last couple of years:
The fuel filter (the old one looked like it was many years old!)
The fuel tank ventilation charcoal filter fitted under the L/H rear wheel arch. It's date stamp showed it was original which would make it around 10 years old!

I still have a lack of power issue which I'm investigating.
The engine sometimes seems fine (plenty of power) and other times power out put is a flat as anything. Basically it is displaying typical MAF failure symptoms that often appear in the Forum. But having replaced the MAF with a new Bosch unit last year (and it's looking like new) I am eliminating that for the moment.

What I do know:
The electronic clutch on the supercharger kicks in at around 1500rpm.
The fuel tank recirculating valve (allows fuel fumes from the charcoal filter to vent into the throttle body) appears to be ticking away normally. Electrical connections are clean. I checked this because I remember it being the cause of similar symptoms on a c230k (can't find that thread on a search now).
The MAF is clean & dry - no oil in the intake side of the system.

With the ignition off the recirculating air flap fitted to Air filter housing sits fully open.
After start-up (which is normal) the recirculating air flap remains in the fully open position position. Supercharger is off at this point. My understanding is that the air flap remains open at low revs (up to say 2000rpm) to allow the engine to breath via normal induction rather than trying to suck air through stationary supercharger vanes.
At around 2000rpm the supercharger clutch engages and it kicks in. I would expect to see the air flap close at this point so that the supercharger output would be forced down the intake tubing rather that back into the air filter box which would in effect neutralise it's effect. What I do see is the flap remain fully open.

What I am unsure of:
Can anyone shed some light on whether the air flap should close as soon as the supercharger kicks in or is it progressive closure as the revs increase?
At what point (RPM wise) would you expect to see the flap close?

Are there any tests I can carry out with a multimeter to check that the air flap unit is getting the signal from the ECU to do what it should when it should?

 

[jamesmc]

Something else I know know on the above.

With the ignition on, engine not running, the recirculating air flap unit makes a kind of humming sound.
On checking the flapper it is being held open by it's motor so the unit itself appears to be alive, although running the engine up to 4k rpm does not see the air flap close at all.

Any pointers welcome.

 

[5pares]

I think a star test or similar is needed to point you in the right direction,i could be due to the secondary air valve at the back of the head being blocked.

 

[Uncle Benz]

The flap should close, even when you rev the engine from under the bonnet. You should see the hose that comes off the flap (the one with a spring wrapped round it) swell as the boost pressure increases. Don't immediately dismiss the flap as broken - its operation may be prevented by the ecu seeing something else it doesn't like. Although you say the MAF is good because it is new and clean, I don't think you can rule it out without getting a good indie to hook the car up and have a look at what is going on - as 5pares has already said. The humming noise is normal. Could be a faulty flap, but they are mighty expensive - get it checked out first.

 

[jamesmc]

Thanks for the responses. I concur with the Indie thing but our location doesn't allow for that too well. I just wish we had an MB Indie down here (South Portugal), let alone a good one. The best we have is the local main MB dealer in Faro. I put the car in for a major service with them when I first got it and asked them to check for any faults. They missed a whole bunch of stuff so not too happy with their workshop, although I do get spares from them at 10-15% discount which is handy.

It's looks as though I may have to bite the bullet and put it in with them just to get the codes read.

Would a duff secondary air valve cause the recirculating air flap to remain open when the supercharger is running?

 

[jimsinessex]

When I had the 1999 CLK230K a couple of points I noted in connection with the Kompressor and the recirc flap were:

1. Whilst the komp clutch did engage at around 1800 revs when revving the car in neutral from under the bonnet it actually could be heard engaging at 800 revs when creeping along in traffic.

2. My understanding of the recirc flap (or waste gate as I prefer to think of it as that is actually it's function) is that it starts in the full open position and then modulates from there to give the boost pressure demanded by the ECU to meet the load required. My komp clutch ALWAYS cut in at 800revs even when only trickling along in a traffic queue. I imagine that the flap would remain fully open in that situation as boost would not be required and then gradually modulate as the throttle position demanded more load from the ECU. This logic suggests that the clutch should engage at low revs even when komp output is not required and only disengage when engine is right down at idle. This would square with the deletion of the clutch on later models.

3. When my ECU failed to send the signal to the clutch to engage that generated a code stating the flap valve had failed when it had not. It was replaced with no change and the original one refitted and found to be ok when a new ECU was installed. I think the ECU has to see the flap fully open to engage the clutch to avoid overpressurisation of the air intake system. I never managed to track down the source of the modulating signal to the flap but would guess it has to come from the ECU. Andy Gayle in Birmingham did the diagnostic work on my car at the time and might be worth a ring. He has a website.

4. I suspect running the engine up to 4000 revs unloaded would not cause the flap to close at all as in neutral the boost demanded would be negligible.

5. Reading the codes is probably the next move but from what has been said so far I would hazard a guess that the fault lies other than with the flap valve.

6. A late thought, as the fault is intermittent could it be a poor connection to the komp clutch at the 2 pin plug under the the plastic shield at the front of the cam cover? A squirt of contact cleaner here perhaps?

Hope this helps,

Jim

 

[jamesmc]

Hi Jim

Thanks for you taking the time to recall your experiences with your late, and lamented, CLK. As ever you input is most helpful.

I am of the belief that the recirc flap is functioning as it should.. or better I say, it is ready to function as it should. It makes the usual (I have now learned from reading the MB world forum also) squeal/hard drive data transfer type noises when the ignition is turned on. The car drives and is reliable. I rarely use it in the week as I have our company car to run around in. Getting teh codes read is a bit of pain around here but I have that in the back of my mind as a 'must do' if all immediately obvious usual suspects are tackled. I'm not throwing much money at the problem (by way of repair by random replacement) mainly my time mostly.

As I have read somewhere the secondary (non return) air valve (fitted somewhere at the rear of the engine and not to be confused with the fuel regeneration valve) should be changed out as a service item and has been know to fail and this give similar performance problems. As the valve is quoted by someone as 'only being about a tenner' and as the car is nearing 10 years old I want to change that as a matter of course anyway. The problem I still have is that I cannot locate the secondary air valve anywhere in the .ru site or on the MB parts software I have. I also tried with the MB spares fellow yesterday to locate oit on their shop sysyem but no success.

Any help in giving me the part number for the secondary air valve for a 1999 W208 CLK230K would be gratefully received.

 

[jamesmc]

Just a wee bump....


Any help in giving me the part number for the secondary air valve for a 1999 W208 CLK230K would be gratefully received. I suspect the part would be the same as fitted to the SLK230K.

I just cannot locate the part number for the part on the .ru site nor via my local MB parts dept (language issue there).

 

[jimsinessex]

I have heard mention of the secondary air valve before but believe it was not fitted to our 1999 cars, I never located it either. One thread described the location very well and as far as could see it was not on my car. I believe it was fitted to later models.

One idea might to be look at the parts listings for later 208 CLKs or even the 209 models if that fails. I haven't time at the moment to follow that up unfortunately.

Jim

 

[busby20]

Hi Jim

Thanks for you taking the time to recall your experiences with your late, and lamented, CLK. As ever you input is most helpful.

I am of the belief that the recirc flap is functioning as it should.. or better I say, it is ready to function as it should. It makes the usual (I have now learned from reading the MB world forum also) squeal/hard drive data transfer type noises when the ignition is turned on. The car drives and is reliable. I rarely use it in the week as I have our company car to run around in. Getting teh codes read is a bit of pain around here but I have that in the back of my mind as a 'must do' if all immediately obvious usual suspects are tackled. I'm not throwing much money at the problem (by way of repair by random replacement) mainly my time mostly.

As I have read somewhere the secondary (non return) air valve (fitted somewhere at the rear of the engine and not to be confused with the fuel regeneration valve) should be changed out as a service item and has been know to fail and this give similar performance problems. As the valve is quoted by someone as 'only being about a tenner' and as the car is nearing 10 years old I want to change that as a matter of course anyway. The problem I still have is that I cannot locate the secondary air valve anywhere in the .ru site or on the MB parts software I have. I also tried with the MB spares fellow yesterday to locate oit on their shop sysyem but no success.

Any help in giving me the part number for the secondary air valve for a 1999 W208 CLK230K would be gratefully received.

Hi James,

I had the same problem with one of my SLK's lack of power etc. and it did turn out to be the problem part you described, although, given what other people have said in this post it may not be the problem.

I have the EPC parts programme on my laptop, so if you could give me your chassis / VIN number I could try and locate the ellusive part, (PM me if you are uncomfortable broadcasting your chassis/VIN number.)

Regards,

 

[jamesmc]

Hi Busby20

I will PM you shortly. Much appreciated.

 

[busby20]

Hi Busby20

I will PM you shortly. Much appreciated.

Hi James, just logged on and got your message, will get back to you asap

 

[busby20]

Hi Busby20

I will PM you shortly. Much appreciated.

Hi James, have PM'd reply with various part numbers, hope these assist

 

[jamesmc]

Thanks Brian.... I have responded and will post here with results when I have them.

 

[television]

You can also PM the VIN number to me, as I have the EPC

 

[jamesmc]

This has gone off topic a bit... my fault.

Thanks to all... and to Busby20 for the part numbers. I have now located the check valve. It falls under the compressor section for the engine. For my car (M111.975 engine) the part number is: A002 140 68 60

Item 38 in the image below.

I have seen reference somewhere that the valve is located at the very back of the engine. In this case (W208 CLK230K) it is mounted to the exhaust manifold side of the engine.

The valve can be be seen by peering down between the exhaust manifold. There is a stainless steel bracket/pipe fitted at this point to which the valve is fitted. I will collect/order one on Monday.

 

[jamesmc]

Back on topic - recirculating air flap

I did find in a thread over at MBworld a procedure for learning in the recirculated air flap. Applies to 203.747 C 230 Kompressor.

AF07.61-P-2000-01A Learning in recirculated air flap actuator
ENGINE 111.981 in MODEL 203.747

1) When ignition is switched off press flap slightly past limp home
position.

90° position must be changed manually. The processor
shut-off delay has a duration of approx. 5 seconds.

2) Switch on ignition for approx. 15 seconds, switch ignition
back off again and wait for processor shut-off delay.

3) Switch ignition on for approx. 45 seconds, switch ignition
back off again and wait for processor shut-off delay.

The learn-in procedure for the recirculated air flap is then
completed.

Comments from MBworld Forum in thread:
http://www.mbworld.org/forums/c-cla...d-air-flap-air-flap-reset-procedure-m111.html

It's a long thread which wanders off track as it goes, so I have quoted some of the more pertinent comments.


On the second step during the 45 seconds wait, you can actually see the flap close up automatically and then open up again - pretty much resetting itself.

I actually just closed the flap a couple of times, and because its springloaded it goes back to its open position, and then I moved to step 2, which was the ignition part. You'll know when its working as an actual noise comes out of the valve, and on the third step (which is the second time you turn on the ignition) my flap actually closed on its own and then opened, telling me that in fact it actually resetted itself.

So I did the flap reset the other day.
I held it slightly off 90 degree (normal position when the car is stopped)
while someone else turned the key.

It seemed to do the reset both times we had the ignition on.
It happens very quickly, opens and closes.
I tried doing it myself, but I have no idea if it worked...by the time you
get from turning the key to front of the car, no way to know if it did it already, so have a 2nd person helps.

I didn't notice a big diff on driving. And the position of the flap after it warmed up for 30-60 seconds (when it's completely closed...which leads one to ask, where the heck is getting air from during that time?)
was still at maybe 30 degrees at idle. I'm still not clear on the function of that flap. When open it pulls a mixture of fresh air, and exhaust off the
oil breather hose. When it's closed it.... ?????
Makes a funny sound! Like it's gasping for breath!


My observations on carrying out the procedure.
I tried this procedure on my car as I couldn't see any harm in doing so, and didn't see the flap close fully nor appear to reset (as in close fully and re-open).

When the ignition is off the flap sits fully open (held open by an internal spring).
When the ignition is turned on the flap closes very slightly and remains in that position being held in place by the motor, no doubt under instruction from the ECU. With the engine running, in neutral, the flap remains in the same position (about 20 degrees off fully open) even when the kompressor kicks in at around 2000rpm.

None of the above takes long, not costs anything, to do but it was worth a go to see what the end result was.

If anyone has a W208 CLK230K and fancies giving the re-learning procedure a shot I would be interested in the results.

 

[television]

just a few things about the electrics.

The actuator motor M16/7 is linked to the camshaft sensor Y49 and the Y2/1 super charger clutch, this is linked to the K40/4 motronic fuse and relay module,a separate fuse K40/4 is used here

Let me have your Email address please james

 

[jamesmc]

Let me have your Email address please james

Hi Malcolm

PM on it's way.

 

[television]

Hi Malcolm

PM on it's way.

It may or may not be of use,but at least you can see all of the wiring, I cant print what things are,but I have put them up here.

I still cannot find one word in WIS on setting the flaps up