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Juddering and losing power

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Could be anything. How many miles has the car done ? Is the engine management light on to indicate a fault ? Is the servicing up to date such as spark plugs, air filter since it may be an air/fuel mixture fault. Check if the air ducting to the engine is ok since an air leak could cause juddering. If the juddering happens when letting the clutch out it may be slipping and need the clutch replacing. When at 3000 rpm does the engine speed still increase but not the actual mph which also indicates a slipping clutch ?


If the car came from a car dealer it ought to have a warranty so the dealer should then sort the fault.

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  • 3 weeks later...

If it is  still doing it, I would ask the dealer if you can take it in whilst it is happening and take them for a drive to prove the fault is real. If it happens when the engine is hot, make sure it is hot when you do this if they agree to it.

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Sorry I should have been more clear


Citroen took the car for a test drive and they know the problem is there but they can't find the why it's doing it.

Firstly they said it needed a ECU software update. Done

Then they said it was the throttle body. Changed

Then they said it was the mass airflow sensor. Changed 

Then they said it was some sort it restrictor as it was not in limp mode. The restrictor was doing it. But no restrictor found.

They have checked all the hoses no rips or leaks.

They have scanned it for codes and nothing has come up.

They have also done a live read everything seems to be working as it should be.

They have advised they would need to strip it apart and have a look at every single wire/sensor etc and they will charge on the hour and it could take upto 3 weeks to check everything.... That could be in the thousands...





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If the engine management light is on there should be a fault code. I would buy a code reader and put the code on here to see what it might mean, regardless of what Citroen have so far checked. There was an odd case on here of a car that was losing power and it turned out to be a blocked exhaust. There have also been cases of water in the ecu wiring/connector/fuse box that gave problems and these can take a lot of effort to find. I previously mentioned the spark plugs since I had a Saab that started juddering when hot and it went after replacing the plugs - one of them must have developed a fault but they all looked ok.

The comment about wanting to charge potentially thousands might just be to fob you off, hoping you will go away since they have not been competent enough to sort the problem.

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  • paul.h changed the title to Juddering and losing power

Spark plugs changed but still the same 

New battery also put in still the same 

Got a code reader but it's not even connecting to the brains of the car tried another one at the garage still nothing.

Been advised by an electrician/mechanic it could most likely be the ECU as the car looks like it's has previously had a front end hit and has been repaired possibly leading to ECU impact damage as the front end needed straightning out.

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You said Citroen had done things that would have required the 16 pin code reader socket to be working so it seems odd a code reader now does not connect. I usually connect one by plugging it in the OBD socket and then turning on the ignition so the dash lights up and the reader will then connect to the various modules. Without the ignition on the reader does not connect. I turn off the ignition before removing the code reader. One of the pins, possibly 16, gives a 12 volt positive supply to power the reader - you could use a volt meter to see if this happens in case a fuse has failed.

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  • 2 weeks later...
  • 1 month later...

Quick update 


Finally resolved the issue of the juddering at 3000rpm.. god fed up with Citroen making excused to changes various parts so took it to a local garage who had the same dealership diagnostic software.


Couldnt read any codes from the ECU as it was faulty been told you can only wipe the codes so many times before it becomes useless.

Well ECU changed came up with throttle body he took that of give it a good clean and lined it back up???? Works better than before no more juddering at 3000 rpm.

Aso been advised car has been In a previous accident on the front end as subframe shows damage. And various repairs marks on front end...

Only issue now is car is shaking/Vibrating  whilst idling drives fine. Whilst idling where should the rpm sit at?? as it's just above the bottom block on the first line on the rev counter

Can rock the engine slightly by hand... Is that supposed to happen????

Also the aircon has stopped working but the button lights up when pressed...

And finally no more central locking...

And thank you to every one who tried to help

Forgot to mention had a new key cut for the car.

Whilst the car was in the garage they had a break in and they stole the safe with the keys in and a few cars luckily they could start my car  as it had no ECU in it 







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Good to see there has been some progress on your car. In some ways it might have been better if your car had been taken, then you might have got another one.

Is the shaking/vibrating whilst moving, if so a first step would be to check the wheels are balanced. Somewhere like Kwik Fit would do that at a small charge.

The air con not working is usually when it needs regassing. Over time the refrigerant gradually leaks out until there is not enough left for the air con to work. It can also happen if there is a leak. Again somewhere like Kwik Fit can regas the air con.

Central locking not working, it might be the remote key needs to be initialised to the car or its battery might need replacing. The handbook should say how to do this under remote battery replacement but on our C5 it is simply putting the key in the ignition so the dash lights up and then immediately holding down the key lock button for more than 10 seconds, then start the engine, stop it, remove the key and then try the remote to lock the doors. Sometimes it can take a few goes or the battery might need removing and putting back in the remote and trying again. The C5 spare key if not used for a long time also needs to be initialised since it loses track of the remote code after so many uses of the other key.

It should be possible to rock the engine slightly by hand but a lot of effort will be needed, if not then the rear engine mounting might need replacing. To get an idea of the effort needed try on any other car.

Idling rpm is usually around 800 rpm on most cars once warmed up. If you do not have a rev counter with numbers, then a code reader that gives live data would show the rpm.


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Hi Paul many thanks for your reply.


The vibrating/shaking only happens whilst idling but driving the car there are no issues.


Had a test rocking the engine on my C4 alot if effort was needed. Rocking the engine on the C1 you can hear a slight knock at the back so most likely it it would be the rear mount just need to get it up an Ramps to have a thorough look at it.


Had a word with the garage this morning they have said they had to change something to do with the key coding box thing (can't remember the name of it now) as they couldn't risk having the car stolen with the old key. Did try what you suggested but but no joy there have it booked in for next week they will sort central locking issue out.

Aso booked in with Kwik fit for an air con check up to determine if its a leak or just need regassing.

But thank you once again for the help really appreciated.







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  • 3 weeks later...

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