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Mike, UK Car Mechanic
Category: UK Car
Satisfied Customers: 39198
Experience:  Hi, I am a Car/ vehicle technician of 34 years. 29of -running my own repair/diagnostic business.
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mercedes benz c 270 cdi I have a mb 270 cdi diesel,auto, 2002.

Resolved Question:

I have a mb 270 cdi diesel,auto, 2002. I used to have terrific accelleration but now at around 50-70 if I press the throttle pedal down I will increase speed slowly and can press the pedal to the floor which makes no difference. I could never press the pedal to the floor before as the car would take off after dropping a gear. My on board computer relays my fuel consumpion is better and the car drives fine, I just miss the accelleration at times on the motorway. The engine surges and hunts which is probably more annoying than the accelleration. The car has been like this for months and is not a major problem but before I used to move the throttle an inch and get results. Now I have to wait till the car picks up speed in its own time. Is this an injector problem. It happened suddenly, not gradually. I have gripped the turbo hose to the engine and it swells up as I rev the engine suggesting the turbo is fine.
Submitted: 5 years ago.
Category: UK Car
Expert:  Mike replied 5 years ago.
Hello and Welcome to justanswer..

What is the mileage you have on the vehicle?

What is its service / recent repair history?

Do you have any warning lights on the dash at all?

Can you feel the turbo come in at around 1800 rpm when driving - can you test for that and let me know...?

Lastly - when you get this problem - lack of power at that range -does it blow smoke..and if so ,what colour?

Rgds - MIKE............................................
Customer: replied 5 years ago.

hi mike, sorry for the delay. my car has covered 123750 miles, serviced regularly and about 18 months ago the epc light came on and engine derated when I tried to accelerate. switching the ignition off cleared the malfunction, but I had to be careful not to accelerate too quickly. This was no. 1 injector which was replaced and fault cleared.

There are no warning lights on and the black smoke I used to get seems to hav e reduced when I accellerate. I did discover something important yesterday. I wanted to check how much smoke was coming from exhaust and when revving the engine to maximum it would only rev to 3000 rpm instead of 5000rpm. The revs cut out at 3000rpm leaving the maximum throttle travel dead.. the turbo appears fine. When I first bought the car It passed the smoke test with 1 rev of the engine as the reading was so low but the last 2 mot's I have to clear the exhaust by revving the engine to get the readings down. The car does 80 mph @2500 rpm and would explain why the accelleration is poor when I put the pedal to the floor as that end of the travel is dead.

Hope this has narrowed down the area of problem.


Thanks, Sandy

Expert:  Mike replied 5 years ago.
Hello again - thank you for your reply.. thats fine.. and the info too which is very helpful..

There are a couple of different things that can be causing what you have here..

Given all that you have described, the air flow meter comes to mind straight a common cause of such problems...

Yes, you could have injector trouble - but its just as likely to be the MAF ( air meter )

You can try disconnecting that and see if that improves / cures it - take the electric connector off - the engine may run badly on idle etc - but if things are better power wise, its a good indication of the Maf being faulty. ( This is the unit in the large air tubing from the air filter )

If its not that - then I have to recommend have a plug in diagnostic test done. This will check for fault codes if it has any -and if not - it can check the live readings as the car is driven - hence any faults will become apparent "on screen".

MOst small garages have the equipment to do these tests for you so you dont need to use a dealer.. Certainly as there are several other things it could be - if its not the Maf.., it makes sense to do that because that will find the fault rather than replacing items which gets very expensive and is a waste of time and money.

So try that with the Maf first..If that cures it - great. If not - have the diagnostics done.. that is the best , quickest and most cost effective way forward on this one for you ..

I'm very pleased to have helped you - but do ask me if you need anything more..

Kind Rgds, MIKE


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Mike, UK Car Mechanic
Category: UK Car
Satisfied Customers: 39198
Experience: Hi, I am a Car/ vehicle technician of 34 years. 29of -running my own repair/diagnostic business.
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