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

[GreenV8S]

If that was me, I'd try to work out whether the amount of fuel going in was changing when the problem happens. Fuel pressure and injector duration are the easiest ways to check that - both relatively simple to monitor with inexpensive equipment.

If you aren't up for that type of investigation then the alternative is likely to be paying somebody else to do it - which seems unlikely to be cost effective under the circumstances.

[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?

[bmwmike]

Which engine??

[Caddyshack]

Speak to Andy Walker at walkers autotech or Richard Barker at Barker’s Motor Works...both top BMW techs turned specialist (say Toby said to call)

[lufbramatt]

When my 530i did this it was the camshaft position sensors breaking down. did the same thing, juddering/stumbling when warm, no codes. Assuming yours is an E46 it's the same engine (M54b30). I got lucky and found a pair of new BMW ones on ebay but supposedly the Febi ones are OEM Seimens sensors with the logos ground off. Easy job to change as they are right on the front of the engine at the top.

Edited by lufbramatt on Wednesday 26th February 09:11

[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

[Caddyshack]

Has it had the injector quality recall? My m135i 2008 had it and bmw replaced 5 injectors.

[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.