My car ran badly for a little while today and a similar thing about a week ago.

 

Normally it's fine, then all of a sudden it started running rough; down on power, needs more accelerator and using more fuel. No warning lights or similar. Stopping and turning it off and on didn't seem to help. Turning it off and locking then unlocking the central locking with the key seemed to fix it both times. It felt a bit like it wasn't running on all cylinders.

 

The rest of the time it's fine. It's got 165,000 miles on the clock, the last 40,000 done by me over the last 18 months. I've always had it serviced by a good independent except the most recent minor service about a month ago which i did myself (I just changed the oil, filter and topped up the power steering fluid).

 

It's lpg converted but I don't think this is the problem - i switched it back onto petrol and then onto lpg again when it was running badly and it didn't make any difference.

 

 

Any thoughts gratefully received!

I had s 635csi that had an issue similar to this. Turned out to be a sensor but I'm struggling to remember which one, might have been exhaust temp or lambda.

 

Problem I had was that for bmw to diagnose the issue, the fault needed to be active when I took it in to the garage. Sods law this took a few weeks for me to be able to get the car to bmw whilst running rough.

 

Try a BMW forum mate, they might be able to offer advice and be more knowledgeable of your specific fault.

Almost certainly one of the cam sensors, my mothers 528i displayed the same symptons rough running, down on power, it will begin to just cut out at junctions and on occasion refuse to start if you don't sort it.

 

It could just be the connectors but the M52's are quite well known for needing sensors

Cheers lads. I have looked at and tried a couple of BM forums but I haven't found a really good one yet as far as I can tell.

 

One did suggest camshaft sensor so that is sounding very possible.

Remember there are both exhaust and inlet cam sensors so there are two to go at and different part numbers IIRC.

 

I have some software I use for my E39 it was only £15/£20 on ebay I think. I use it on my M5 and also used it on the 528i as well with the older round connector for the diagnostics port