Urgent help - W208 strange engine revving

mtayre

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Jul 13, 2007
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Hartlepool
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CLK 320 (W208)
Hello All,

I'm in need of some urgent help. I've got a long journy tomorrow and the car has started behaving oddly.

On startup the engine seems to be over revving but just slightly, about 1200 rpm, which it usually does when starting from cold before dropping down to around 700- 800rpm on tick over.

Today however it's not dropping off. When pulling away the engine is revving randomly and when stopped and put back into park, it is revving up to about 3000rpm and then dropping back off to around 2500rpm and keeps revving up and down between the two until switched off. Does anyone have any advice on what this could be?

Thanks
 

Benzmanc

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I had something similar on a TT and it turned out to be a lambda sensor. I would suggest you get the car on a STAR machine though. I found my fault by unplugging the lambda which settled the idle immediately, not sure if that would work for you.

Daz
 
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mtayre

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CLK 320 (W208)
The airfilter was replaced on it last service about 2000 miles ago. I can't see any obstructions or blockages to the airflow. Any further advice?

Thanks
 

brucemillar

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I'm no expert. Vacuum leaks can cause hunting. You could have a look for a split/perished hose. Spraying damp start along hoses with the engine running can be a good indicator. Revs will flare when you spray a hole. Other than that it may be you need to get it plugged in to a STAR.
 

dog68

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Unplug the maf sensor, if it then runs normal, you know its the cause, worth a try.
 
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mtayre

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CLK 320 (W208)
Is it just unplugging the cable going into the MAF or do I need to remove the MAF from the pipe? Also what should i expect from the engine when unplugged? is it going to be normal tickover?

Thanks
 
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mtayre

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Hartlepool
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CLK 320 (W208)
No joy with it, unplugged the MAF sensor and the engine ran really lumpy, as if it was missing although the revs we about where they should be. Any further ideas or is it a trip to the indie for STAR?
 

BlackC55

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Don't unplug the MAF. It proves nothing at all.

I suspect the throttle bitterly maybe sticky. Are you able to remove it and clean it?

Also disconnect the battery for 30 mins. When you re connect it leave the ignition turned to position 2 for twenty mins but don't start it. Turn off then start.
 
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mtayre

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CLK 320 (W208)
How would I remove it to clean? Not that technical and don't want to break anything more than it already is.

Thanks for the help.
 

BlackC55

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Take the intake pipe off down to the butterfly and then just unbolt it.
 

flango

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Did I miss something? What engine are we talking about we could be dealing with a CLK 200 or CLK 55. :dk::dk::dk:
 

flango

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Good point. I assumed it was a 320:eek::rolleyes::doh:

Strangely enough I always assume a 230 :doh: but that's probably because I have one :D Just thought I was having a senior moment and missed the engine size :D
 
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mtayre

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Hartlepool
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CLK 320 (W208)
Yeah I should have said it is a 320 but it's all sorted now. Got it to the indie and got the below error codes:

(p202E)M16/6 - Throttle valve actuator - line mixed up / positioner fault (P0120)

(P202B) Idle speed control implausible (P0507)

(P20D4) Load limit active

P2006-002 Intake air temperature sensor (B2/5b1) under correction of injector mixture (P0170)

P2004-001 - Hot film Mass Air Flow sensor (B2/5) Short circuit to positive / open circuit (p0110)

The codes were all cleared and the car tested and it's running fine, no codes have returned.

Thanks for the help though.
 

Alecko

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Aug 27, 2009
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Can anyone help.I recently ran through water in my Feb 2002 E class and almost immediately BAS light came on an car went into limp mode.Rac and garage diagnose Throttle actuator and due to high cost of repair Ive claimed insurance.Initial signs they are saying it is mechanical failure.Is it possible for this situation to have been caused by water .My car is well maintained and was last serviced in October.Im desperately needing some advice.Thanks Alecko.
 

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