Juddering when braking

Hi, I'm new to this forum and a bit naive when it comes to cars, so please be patient!

My Nissan Micra K12 2005 reg 1.2L auto has recently started juddering when I come to a standstill, for example at some traffic lights. Sometimes it's bad, sometimes not so much. I was low on oil last week, so I topped it up with some Castrol fully synthetic 5w30 oil and thought that might solve it, but it didn't. It only happens once the engine is warmed up, and when I rev, it briefly goes away. I had the full service and MOT last Friday and they changed a wheel balance and replaced the spark plugs, to no avail.

The local (not Nissan) garage said it was an idle misfire. and that the coils may need replacing, but they didn't want to go ahead with it as it cost an additional £80. Having looked at several Google results, it seems that it could be that it needs a new set of coils, or it's the airflow meter in the throttle body, but I don't know for sure. It could be something else, but I keep worrying that the car will die on me. They said to get the MOT and service done (which I did) and they put some fuel additive in so that I could drive it on my planned trip from Essex to Northamptonshire and back again yesterday to clear any grit or build-up, and it ran fine, but obviously it juddered at a standstill.

I have a one-year AA warranty which runs out at the end of this month, so I intend to try using that to pay for whatever this could be.

Does anyone know what it could be?

Thanks!
 
You need to get a code reader on it. Errors 301-304 are misfire on cylinders 1-4. If you get a code, swap coils 1 and 2 and coils 3 and 4 and reset the code. Test it again and if it's changed, you know which coil is duff. I had a bad misfire which turned out to duff no.3 injector but I had different symptoms.
 
Okay. Not being an expert...how do I do that exactly? Do I take it to a dealer?

Is it going to be safe to drive for the time being?
 
Should be ok to drive. A basic code reader from eBay should be around £20 or £30 :).
 
A fortune but you'd only need to replace the duff one if it is a coil :).
 
Thanks Guy. I've spoken to both the garage and the AA sales team. He can't think of it being anything other than the coils, and both said it should be covered under my AA Gold warranty. Do you think it will be?
 
The car is with Halfords now. They've run a diagnostic test and the only error coming up is the camshaft, but they've examined everything and all the readings are fine. They are waiting to hear back from their technical guy. They haven't changed the coils yet.

Hope it's not going to drag on for much longer...
 
It wasn't the coils in the end, but indeed the canshaft sensor! Error P0011 came up, so they replaced the solenoid, cleaned the camshaft sensor and cleared out any excess oil or dirt that was stopping airflow. Drove it home, got to a standstill and at long last, the juddering has gone! Hooray!
 
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