Hi total noob to Mercedes here, please be patient.. Just got the car, in nice condition, however when out driving I have noticed that when decelerating the engine "Surges.." as if I am tapping, or blipping the accelerator and the car surges a little with each "Blip.." .. Every two or three seconds..? - Happens all the time.. Thought I could live with it, but now I feel ready to pull some spiders legs off.

Can anyone help me on this problem? (Not the spiders legs thing, but the car..)

BTW this is our first mercedes ever, and I must say we love it, dont know why we didnt get one years ago, what a unique ride they are. If I wasn't an enthusiast before, well, I'm going to be one soon...! Opening the bonnet of this was a little daunting as there's nothing I can say I recognise straight - off, apart from blindingly obvious things like oil and washer reservoirs..are there any resources for workshop guides etc. anywhere online?

R'gds..

John.

 

With your symptoms.

Have the Mercedes dealer inspect the intake manifold air flaps, they are a constant common weak point on the CDI.

roy@pelicanparts.com


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I've meanwhile enlisted a friend of my brother's to look at it he's a diesel mechanic. (Actually runs a diesel specialists shop..) He'll be on holidays for another 10 days, but he's a reliable guy.

He's already formed a (Telephone..) theory of a leaking vacuum pipe/seal which I half suspected, but he needs to hear and diagnose it for himself...

But he will be interested in this Intake Flap idea too. Which could turn out to be not too expensive to repair either.. Hmm.

Are they metal those manifold flaps? or some nylon/plastic? I must say I've never heard of them breaking through either wear or abuse in many, if in any other engines at all.

B'rgds..

John.

 

the intake plastic flaps are a big problem on the cdi....its used for engine breaking and smooth air intake using the swirl method....changing the manifold is a fairly big job but i would try using a diesel air intake spray from the egr side and this will help loosen and clean the carbon deposits that cause the flaps to stick and cause the problem.....also its controlled by a electric servo motor mounted under the manifold that go bad and is connected to the flaps by linkages you can look deep under and see if these are all working as you rev the engine up,its like a rail with links to each flap and these can break away....they should all work together and if not you have found a problem that could also cause you problem you described......hope this helps.

 

Thanks for that extra info Coolish, I'll have to wait until the guy comes off holiday to get a proper diagnoses, but this is all great information that we'll be checking out when the guy starts work. I promise to post back the findings/results as soon as I get some.

I have noticed that fuel economy is a little poor at the moment, around 28 UKM to the gallon, and I'm hoping fixing this problem may well help there.

 

no worries good luck. .Regarding mpg if these flaps are not working correct it would have a big impact on using more fuel.