Engine Judder when warm BMW330i

[gquanne]

Specifically:

BMW330i. engine juddering - only after 7/8 miles (engine warm). Mpg goes through floor when Juddering and high petrol use. Intermittent even when warm.

Just around the first time I noticed the problem I got faults "Catalytic convertor at bank1 and bank2 below threshold". However I'm thinking this was a symptom rather than cause as the code was cleared and has not returned with over 600 miles driving + 2 cats going simultaneously. Now no codes are being thrown up, The car as 247k miles and have now bough a new car so I'm not looking to spend £1000s trying to sort this,

I'm going to check my ignition coils but I'm doubtful as no misfire codes
I'm going to replace the MAF sensor albeit with a used bosch one - yes I know, but figured better then cheap chinese effort and generally find used parts to be okay. + it's £18 and not £300

Already changed one upstream lamda sensor, but again no codes anyway

Considering a fuel filter change

Any other likely causes? please consider the specifics of the problem?

Many thanks

[gquanne]

I can see the mpg on the computer dropping significantly when problem arises. And over more fuel being used as a result. Would MAF be a possible due to this or more likely injectors?

[gquanne]

Hi all. thanks for replies. It's the n52 engine on 57 plate.

[gquanne]

I've bought a camshaft sensor - cheap and easy to replace and from what I read with it having a control element over to fuel injectors/ fuel usage its a good shout. There's two but it's the same type sensor so i'll try both positions. I report back after the weekend.

Thanks

[gquanne]

Might have been done before my ownership. No open recalls on my car. It was recalled for the wiring issue couple years back. A problem that could lead to failure of the aircon fan. My aircon fan had just failed but of course they decided it was unrelated and wanted £120 just to "have a look". Changed it myself £17 and 15 mins work.

[gquanne]

Hate it when topics not closed out so here it is: Checked all ignition coils - okay and changed intake camshaft sensor and MAF - no joy. Car was sold as is to a buyer that was told about the problem.