Coruscator

Hi

Had a weird one earlier. I suddenly found after driving for an hour that there was significantly less power than usual.
The car runs ok and even climbs up to nearly 80mph but just really slowly. Almost like the turbo isn't working anymore.
I pulled over switched the car off, removed the key, waited a few minutes, started her up again and she was fine
again, as if nothing had gone wrong.

Its happened to me twice now, no warning lights or indication of what is causing it, it even says 'no malfunction'
on the dash. Please help. Whats going on here?

sailorben

I have had this twice in my 2005 CLK 270cdi. I had that car from April and it happened twice through till I wrote it off in December.

I do not know what the issue was, but I also felt exactly what you describe. Both occasions were unrelated. One was accelerating up a very steep city hill.
That was the first time. I pulled over, red lined her out of gear for a bit, and drove off. All was fine. For a couple hundred meters. Then the same thing happened again. I ended up turning off the engine. And that solved it. Many months after, I had a recurrence, and that was driving around 70mph on the M'way I shut off whilst driving and resumed immediately. And all was good. Never happened. No fault codes, nothing. Car was perfect besides those two occurrences. Very nice engines the 270 turbo.

It was a manual, so I knew gear choice wasn't responsible for the sluggishness up the hill.
AND I was getting turbo spool on lifting throttle, so the turbo was functioning.

Sorry I can't advise a problem, but these were my two experiences.

sailorben

(Also Welsh, I see... ��) how long have you had the car? What year is it? I have been quite familiar with the Welsh market this last quarter, sine I'd been looking for a replacement.

Rudeney

I wonder if your transmission was in "limp" mode. When this happens, it lock in 3rd gear. It's very sluggish on takeoff and acceleration. but it will "get you home". You won't get an MIL, but pulling codes from the TCU can give you a clue. If this happens again, try using the TouchShift to manually select a gear. If it doesn't change, then you're in limp mode.

Coruscator

She's an '04 avantgarde, and a very nice example too (if I do say so myself.) Ive has her nearly 2 years now. I'm the second owner!

Eek! You wrote yours off in December? I'm so sorry for your loss.

Redlining? I couldn't do that to her, shes too good to me for that.

Coruscator

Ahh that sounds more like whats going on. It certainly feel's like something is electronically preventing the acceleration.
When I put my foot on the pedal there is a slight surge then it drops back to slow progressive acceleration.

Definately not the usual: foot down, pause - while the turbo spools, (which I like to think is the navicomputer calculating the
coordinates so she can safely make the jump to lightspeed), then off like the scolded cat that im used to!

I didn't think about using the touchshift, grrr. Tried everything else though, kick down, S to C on the gearbox, taking her
in and out of neutral. Thanks, if it does happen again I'll try that.

I did have a 'B' service about 6 weeks ago and noticed they didn't list gearbox fluid on the bill. Is that something that
should have been done with a 'B' service?

sailorben

Yeah, unfortunately, my manual 270 was totalled in December, but I've got another, this an auto.

I know exactly what you describe, but I can't see a manual transmission going into limp mode! So that wasn't the case with mine, and when on the motorway, I was at 70 and quite could accelerate, all be it slowly but smoothly, up to 80/90, which surely wouldn't have occurred if the car was in limp.

I know the two cars are individual, and mine isn't the one having the issues now, but this really does sound exactly what I experienced in my 270.

Rudeney

Transmission fluid and filter is not part of a B service. And actually, on the 722.6 5-speed, it's not a part of any service as it was sold as "sealed for life". However, it is unofficially recommended to do this every 70K miles. On that transmission, all you can do is drop the pan and change the filter, then refill with about 4 quarts (less than half of the total capacity). There is a flush procedure but that requires and additional 9 quarts.

Regardless, dirty or even low fluid generally won't cause limp mode. Low fluid can cause the transmission to shift harshly or drop out of gear, which can in turn damage parts and then cause limp mode, but that doesn't seem to be your issue. The most common cause of limp mode is a bad conductor (a.k.a. contact) plate. This is the electrical part inside the transmission that transfers signals from the TCU to actuate the hydraulic valves, and also contains the speed sensors. If a speed sensor gives an erroneous reading, as is the case with a bad conductor plate, the TCU will activate limp mode. This is a common problem on these.

My advice is to just keep driving it. It may never occur again, or once again in a few years, or it may get steadily worse. If it does get worse, then it's not a horrible DIY on the 722.6, and the part is not terribly expensive. This is good news compared to the 722.9 7-speeds, which have the same problem. On those, the TCU is part of the conductor plate which not only makes it more expensive, it becomes a dealer-only job as those require SCN coding.

Coruscator

OK.

Update!

Just came back from a 4hr drive and it has happened again. Sudden loss of power just like before.
So I did as you suggested and manually changed up and down the gearbox without any problem
and it didn't have any effect on the 'loss of power issue'.

Again the fault cleared itself after I switched her off removed the key and re-started her again.

I suppose this means the fault isn't with the gear box after all then.


Hmmmm, any ideas or suggestions gladly received.

Rudeney

So, when you changed gear manually with the TouchShift, did it actually downshift or upshift? If not, then that sound like "limp mode" and you need to get codes pulled from the TCU (a generic OBDII scanner won't do this - you need SDS or other specialized tools for the MBZ-specific systems).

Coruscator

Yes, she did change gear with the touchshift. Up and down the gears.

Rudeney

OK, so I don't think it's the transmission. I'd pull codes - even if the MIL is not illuminated, there may be some stored.

Coruscator

Ok so, had a friend look at my car and he checked the transmission fluid.

It was clean, clear and at the correct level, so sometime before I bought the car this must have been changed.

He then suggested that it might be the Lambda sensor.

Does this make any sense to you guys? Could this sensor be the cause of my woes?

Rudeney

Lambda sensor = O2 (oxygen) sensor. A bad one would almost certainly throw a code.

Coruscator

Ok, the plot thickens. My man put his diagnostic kit on the car and it returned only 1 fault,
which was to related to the automatic heater booster.

His advice was to wait for the fault to show itself again and take the car back to him while
it is still faulting and in limp mode.

I suppose this doesn't shed any light on a solution. :0(

polda

have you found the problem? i have same sometimes on my 270cdi .. thx

Coruscator

Yeah, it was my MAF sensor. I took mine out and cleaned and refitted it.

The loss of power problem never returned.

If this doesn't work, then I would replace it with a new one.

Don't buy a cheap one its a false economy.

Pierburg are OEM and they are about £90.

Reanimation

Nice easy fix, How may miles has the car done?

Coruscator

Mines done 120k.

But when I bought the car 3 years ago the garage put a new MAF sensor in.
One of the warning lights was lit on the dash (can't remember which) when I
took her for a test drive. So they renewed it.

Spence83

I have a 2004 270CDI AUTO and yesterday for no reason the fan went to full speed, dash engine temperature went to 130 degrees and major lack of power, had to move the car by shifting manually. Left the car over night so then engine temperature was very low, but immediately putting the ignition on the fan was running flat out and engine temp on dash display was still 130 degrees. would a faulty coolant temp sensor put the car into limp home mode?

Rudeney

Yes, if it was at 130C on a cold start, I'd say you have a bad temp sensor.

Spence83

I disconnected the coolant temp sensor and the fan was still running flat out, but guessing this is due to default running due to no signal.

Coruscator

Ok so limp mode got more frequent so...

How difficult is it to change an air inlet manifold on a clk 270 cdi?

Went to the stealership today and got quoted for one.

It is suggested that this will cure my car from going into limp mode.

Any Ideas on where to get these parts from?

A 026 997 43 480 C28027 Seal Ring
A 611 094 01 80 C02021 Gasket
A 611 141 02 80 C13031 Gasket
A 612 090 19 37 F07810A Air Line


As always, thanks guys