Potentially dangerous gear change issue

BruceMonty

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E320 CDI 2007
I have an E320CDI on a 57 plate. It has an auto gearbox with Tiptronic. I have had an issue for some months now that Mercedes have tried to rectify three times with no success.

The issue occurs when the auto gearbox cannot decide which gear to select. This used to happen under hard acceleration, but now occurs even when acceleration is moderate. The gearbox eventually selects a gear, but then has no acceleration. I can literally mash my foot into the carpet, but the car will only get faster at a rate of 1 mph every 5 seconds or so. The only way to rectify it is to pull over, shut the car down and restart.

I have tried moving the gearbox into Tip mode when this happens, but although the car changes gear, the acceleration is still not there. Has anybody come across this before? The result for me is that I can no longer trust the car to accelerate - it is that unpredictable.
 

television

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Hello and welcome, I think that your car needs a new MAF sensor, cheapest from any Bosch service center and halve the MB price, you can sometimes unplug it and try the car to see
 

jberks

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Does sound like the ECU's selecting safe mode. Not really a gearbox issue at all, just that the engine has switched to reduced power, which also turns off the turbo and switches off kick down. Could well be the MAF as Malcolm says but odd that MB haven't sussed it as it should show up in the fault codes and also on a live reading.
Perhaps they're being thrown by the description of the issue being gearbox related. Does the above ring true?
 
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BruceMonty

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Thanks for the advice guys. In answer to your question jberks, yes, what you describe certainly sounds like what is happening. When I have spoken to the Merc garage that has been dealing with it, I have explained the issue, and their take was that it was something to do with the engine management system?

They replaced a part last time that they said should cost me £500 as the car had just gone out of warranty, but as a gesture of goodwill they would only charge me half of it. Needless to say, I told them where to put their kind offer, as this fault had been reported at least twice whilst the car had been in warranty. Does that sound like the sort of price a Merc garage would charge for replacing the sensor you mention?
 

rjevon

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My ML270 MAF cost me £68 froma main dealer..

So I doubt that was what they were going to replace at that cost.
 

Naraic

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My ML270 MAF cost me £68 froma main dealer..

So I doubt that was what they were going to replace at that cost.

And they are a plug and play item which you can easily do yourself.
 

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Yes they are just plug in and away you go, if you have been unlucky, the change in the mixture due to the MAF giving incorrect information could have shifted the O2 sensor and this can put the engine lamp on. Once the new MAF is fitted the lamp will more than often go off again as the O2 sensor gets back to its stored position.

The MAF is one of the only parts that will reset , when you turn off and start again, this is often the clue
 

dieselman

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Thanks for the advice guys. In answer to your question jberks, yes, what you describe certainly sounds like what is happening. When I have spoken to the Merc garage that has been dealing with it, I have explained the issue, and their take was that it was something to do with the engine management system?

They replaced a part last time that they said should cost me £500 as the car had just gone out of warranty, but as a gesture of goodwill they would only charge me half of it. Needless to say, I told them where to put their kind offer, as this fault had been reported at least twice whilst the car had been in warranty. Does that sound like the sort of price a Merc garage would charge for replacing the sensor you mention?
You need to find out what the codes are, but my guess says inlet port shutoff motor or EGR valve.
 
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andy@pcd-ltd

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On some of the 280 and 320 suffered with parts of the exhaust manifolds breaking of damaging the turbo.

I have driven a vehicle with this fault and it can cause irratic gear change and limp mode.

As alex says you need to get the fault codes and post them on here
 

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You need to find out what the codes are, but my guess says inlet port shutoff motor or EGR valve.

On some of the 280 and 320 suffered with parts of the exhaust manifolds breaking of damaging the turbo.

I have driven a vehicle with this fault and it can cause irratic gear change and limp mode.

As alex says you need to get the fault codes and post them on here

But the fault goes away on a restart
 

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It will only switch from current to stored Malc, but will still be there!

But if the EGR is open, it will be there irrespective of any data, the same with a damaged turbo, it must be the MAF
 
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andy@pcd-ltd

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With the damaged turbo the fault will disappear as you will be resetting the ecu when you turn off the car like you do most times when the car goes into limp mode.

Then when you are driving again the car sees the difference in the engine data and selects limp mode again
 


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