pekak62

I've a C220 CDI, August 2007 build date, with an unusual problem which MB of Melbourne cannot seem to be able to fix.

After being in absolute denial, they finally and grudgingly accepted that there is a problem with my car, and at least one other.

From day one, on start up, the engine would idle at 750rpm, irrespective of whether it was at optimal operating temperature. Turning on the heating to anything higher than 18C would cause the idel to go up to 950rpm (which is normal I believe but only when the engine is stone cold - once warmed, the idle should revert to 750rpm). But on my car, the engine would forget to revert to 750rpm. The only way to 'fix' this was to do a hard reset, i.e. turn the engine off and start again). Having done this the engine would not become confused again about its idle rpms.

Worse, driving home in the evenings, after about 200-300 metres, AND irrespective of whether the heating or a/c was turned on, the engine would shift its idle from 750rpm to 950rpm AND, again would only behave properly if a hard reset was done.

After 4 separate attempts, car went in for a week and during this time I drove a replacement 220 CDI, build date May 2008. Less of a problem, but on occassions, even this car would forget to revert idle to 750rpm after the heating and a/c were turned off.

My own car - they reset everything and it behaved well - properly idling at 750rpm and returning to this after the heating and a/c were turned off - for about 2 days.

It's now back to its nonsense of idling at 950rpm at every opportunity with the only way to correct this - yes, by doing the hard reset.

Has anyone else experienced this problem, and hay YOUR delaer been able to fix the problem?

I drove the W203 220 CDI for about 3-4 years (I forget actually how long, now) and never had this problem.

Apart from this idle problem the car is great - I can even get 5l/100 kms on a long trips!

Paul Rozario
Melbourne, AU

Carsy

[QUOTE=pekak62;2965140]I've a C220 CDI, August 2007 build date, with an unusual problem which MB of Melbourne cannot seem to be able to fix.

Hello, I have an Oct 08 220 CDI build date & have not experienced this problem. I will be very interested to know how your problem is resolved. John from Taree NSW Australia.

Ausmbtech

I've never heard of this problem either.

Due to everything on these cars being so interlinked, the engine control unit, transmission, a/c and battery control (on applicable models) can adjust the idle speed as required.

If they haven't already done so, i'm sure they have, I would get the dealer to "flash" the engine control unit, transmission control unit and A/C control panel and see what happens from there.

I would certainly want it fixed too, but it may take some time. MB admiting there is a fault is the first step though, make sure you allow them the time they need to experience the fault for themselves as intermitant faults can be very frustration to both owners and MB techs.

st13phil

Hi Paul,

I don't know whether or not this helps, but here's another data point for you. My C220CDI was built December 07, but the ECU was updated to latest software in March 08. It's an auto, BTW.

With the transmission in "S" mode and the climate control on auto at 22-degrees the engine idles at approx 850rpm on the tacho. If I switch the transmission to "C" mode then the idle drops to approx 700rpm. I just experimented with the engine hot and found the following:

Initial condition: Transmission in "S" mode, climate control on auto at 22-degrees, transmission in "D". Idle speed 850rpm. Move shifter to "N" - idle speed unchanged; move shifter back to "D" - idle speed unchanged.

With transmission still in "D", switch off climate control - idle drops to 700rpm. Still with climate control off, move shifter to "N" - idle speed remains at 700rpm.

Once idling at 700rpm two different things happen if I hit the climate control "auto" button to turn it back on. If transmission is in "N", idle speed immediately increases to 850rpm; if transmission is in "D" when I switch on climate control, idle remains at 700rpm, but raises to 850rpm if I move the selector to "N" or if I drive off and then stop again.

If the transmission is in "C" mode then the idle speed remains at 700rpm whether trhe climate control is on or off and regardless of transmission shifter position.

How does this correlate with your car?

hadjionm

Hi Paul,

I also have a w204 c220cdi auto. It is a June 2008 build. I have noted the following....

For the first 3 months, since getting the car in August, the idle speed was about 840, but not steady. The needle on the rev counter would move around between about 820 and 860, say. This was always the case, whether the engine was hot or cold, in S or C mode.

About a month ago I noticed it was idling at about 740, again with the needle moving between about 720 and 760 range. Carsy suggested I try and see the effect of the A/C being off or on, but this made no difference.

After about a week the idle speed jumbed back to 840 (plus or minus 20). It has stayed there until about 4 days ago. Now it is back at 740, but now it is dead steady, hardly any movement in the needle.

Should I be worried? I'm not sure what the issue is with idle speed.

Regards Matthew

Carsy

There does seem to be an unexplainable change in idle revs. I ask the question , how does this change affect the drivability of the car? . Is there increased vibration , is there any adverse effects ? . If not I would not be too concerned. Just enjoy the 5l/100 km fuel consumption, the 125Kw of power & the 400 Nm of stump pulling torque.

Diesel Benz

I have not been reading this forum at the time of the first post but it does sound to me as if there was a SW error in one of the related control units.

Unlikely any harm like vibration or so but if normal idle rpm is not applied when it obviously should, I would look at a fix.

The shop should try to figure out which units are involved with the rpm increase and decrease, it could be the AC control unit requesting higher rpm and the "release" message getting lost. Some CAN-bus messaging issues have been seen for other cases where the ECU update has fixed it.

Fault codes should exist but those may be pretty misleading.

I would have wanted to see more accurate description from pekak62 about the car increasing rpm when approaching home. I don't see why it would be caused by approaching home and not happening elsewhere at similar conditions.

JimPap

Phil's problem sounds directly related to which transmission shift program is active.

The other's all sound like the a/c is signaling that the compressor is on (which normally would drag down the RPM) when its not. Or its low on freon and is not dragging down the engine as it should.

dragonii

Having a 320 CDI engine, I've noticed that, when burning the particles on the diesel particle filter together with an awfull smell, the engine idle RPM are raised to about 200 higher.

Could be an explaining factor...

ctgilles

Mine does it too. But still judders less than the X5, noticed this 'bug' on lots of diesels so I stopped caring.

5 litres?!? Make that 8-9... Not anywhere near as fuel efficient than the Beamers over here. Wish I had waited a month longer for that C250 CDI

Carsy

[


5 litres?!? Make that 8-9... Not anywhere near as fuel efficient than the Beamers over here. Wish I had waited a month longer for that C250 CDI [/QUOTE]

Country driving ie 100 km /hr without the A/C on I easily achieve 5.3 l /100 km. On one trip with tailwind I achieved 4.9 l /100 km.
Overall with a mixture town/country I average 6 l/100 km.

ctgilles

That's strange Never get anywhere under 8, even with a gentle right foot. Must be my driving then. Maybe it'll drop after the first big service...

Diesel Benz

I'd like to see you driving, or perhaps not, perhaps I don't want to be anywhere close to you.

I'm getting an average of 8.2 l/100km with my W221 CDI. With my W211 the best I've had was 5.0 l/100 km (90 km/h, steady speed on a highway).

Either you are doing a lot of city driving (8 l/100 km can be OK) or there is something wrong with the car.

JimPap

What does that convert to?

Diesel Benz

Which one? No need to convert, the figures are already in litres per 100 km.

My tool says:
8 l/100 km = 29.4 mpg (35.3 imperial gallons)
8.2 = 28.7 (34.5)
5.0 = 47.0 (56.5)

zoranv12

Hi,
exactly the same thing in my case. Same car, model year 2008, made in dec 2007, Auto. transmission --> 5Gtronic;
In C mode about 750rpm, S mode about 100 more...same thing with shifting from D to N and so on...
Probably that's normal I think...By the way, I live in Slovenia, car was made for Sovenian market, bought in Slovenia. Consistency at failure I belive if that's not how it suppose to be

Mohameed Abd

Did you solved your problem ? i have the same