Losing power while driving

Hi,
I purchased a c3 a couple of weeks ago, it's a 1.4 diesel and I've had a few issues with it.
I took it back to the dealer a couple of days ago because sometimes while on motorways and dual carriageways it would randomly drop down in revs. Then eventually it dropped down that much the engine stopped, the battery warning light came on, power steering went and lots of error codes appeared.
I called the AA out and they couldn't see anything wrong with it, by this point it was managing to start but before that it wouldn't. The AA couldn't find anything wrong with it apart from 9 error codes which they wiped then left me.
I'm the short journey between there and the dealership it cut out another 2 times.
The dealership repaired the broken electric window I told them about and said they couldn't see the issue with the car cutting out and despite the engine light being on when I dropped it off it had apparently gone off overnight.

So basically the dealership doesn't appear to know what's wrong with it. I don't know a lot about cars but I know it's scary when it just cuts out on a busy road.

One thing I did notice though is that there is a lot of oil in the engine. Do you think it's possible that too much oil could cause performance to be affected at higher revs?
That's the only thought I've had. Any other ideas would be hugely appreciated.
Thanks
Ste

Then this morning I've got in it and it made it to the first roundabout and stopped. Managed to push it onto the grass verge.
Tried starting it again and it tried to stsrt but wouldn't. Then it stopped even trying to start, simply just made a click when I turned the key.
I unhooked the battery for a minute. Still no luck. Sat in it for another 5 minutes, tried again and it started. Managed to get it to make the short journey back to my house.
There's no way I can drive it all the way back from the used car dealers I got it from

Welcome to the forum Stevo871

Stevo871 wrote:The AA couldn't find anything wrong with it apart from 9 error codes which they wiped then left me.

These 9 codes could have been the key to why the car had problems. The car stores error codes when it detects a problem. The AA wanted to get you moving again, rather than diagnose the problem. Wiping the codes was right for them, but wrong for a long term solution.

Stevo871 wrote:I'm the short journey between there and the dealership it cut out another 2 times.

Good, its should be storing codes now, or the lack of stored codes can indicate an issue too.

Stevo871 wrote:The dealership repaired the broken electric window I told them about and said they couldn't see the issue with the car cutting out and despite the engine light being on when I dropped it off it had apparently gone off overnight.

They didn't read the error codes?

This is the first thing to do. Use a cheap OBD2 reader from ebay, or one from, say, Amazon.co.uk or a more expensive and fully featured lexia-diagbox system.

Use the tool to read the codes that have put the engine light on and all the codes that didn't and its possible to use these to diagnose the parts to check to fix the problem.

Stevo871 wrote:One thing I did notice though is that there is a lot of oil in the engine.

The oil level on the dip stick must be between the min and max marks on the dipstick with the car on level ground and a cold engine.


https://citroenc3owners.com/petrol-citro ... t1212.html

Stevo871 wrote:Do you think it's possible that too much oil could cause performance to be affected at higher revs?

Too much oil will damage the engine

Stevo871 wrote:So basically the dealership doesn't appear to know what's wrong with it. I don't know a lot about cars but I know it's scary when it just cuts out on a busy road.

You could just take it back and get your money back because they sold you a car that doesn't work.

Stevo871 wrote:ried starting it again and it tried to stsrt but wouldn't.

Wouldn't turn over or it turned over, but wouldn't fire?

Stevo871 wrote:Then it stopped even trying to start, simply just made a click when I turned the key.

Flat battery? Faulty solenoid on the starter motor, poor power or earth connections?

The first thing i'd check would be getting them fault codes!!!! and you could manually check oil,air flow, fuel flow then the egr valve if it turning and not firing its either too much of one or too little of the other i.e loads of air and right amount of diesel could point towards an egr that's sticking but it would be more apparent on town running.
How much is a lot of oil as above it needs to be between min and max on the dipstick im assuming you know basic car maintenance? if not park car on flat engine off leave for a minute or two take out dipstick wipe clean reinsert and slowly pull back out then you should have a reading of how much oil you have.
Too much oil will ruin your engine and end up being burnt in the chambers and this would ruin your catalytic converter but you would expect a fault code to be shown for that but being a sensor it measures the amount of pollutants in the exhausted gasses and gets engine to alter accordingly.
Failing any positive improvement id happen look into returning the car to the garage.

Hey everyone,
Thanks for all your help, Just an update on this, eventually the garage the car dealership used managed to solve the problem.

..... Cam position sensor....

They replaced that and I've not had a problem since. Quite relieved it was something as simple as a sensor. It's just scary that a sensor can cause such issues.