fuel trim Bank2 misfire 4,5,6

Hi I have a problem with my 530i. Drivess grest but throws up fault code Fuel trim Bank2 misfire 4,5,6. What doe this mean tried to ask the dealers apart from pluggging into their machine did'nt want to know. I have a feeling it could be the coils or Air mass but need to pin point otherwise I'm out a lot of cash. Any suggestions appreciated Thanks John

Hmmm, could well be a coil fault? have you had this plugged into your own obd-II diagnostics?

How is the fuel consumption? is it using more than normal? Ive heard of oxygen sensors throwing up this fault. And there is two on your car from memory... These generally do not throw up fault codes, as they just lose efficiency and not necessarily stop working...

if the oxygen sensor looking after banks 4,5,6 is less efficient, it may cause the faults that you have meantioned....

Mightybmw

Hi Mate,

Where did you get the error codes read? an EOBD scanner or BMW specific?

A fuel trim fault? I would firstly look for any air leaks around the intake, especially around bank 2.............seen this fault many times, especially on the 4 pots.........and its always 1 or 4 possible causes:

Air Leak
Crank case vent valve
MAF Sensor
O2 Sensor

on yours, I would be more inclined to think that you have an air leak.

But to be honest, you do need to get the codes read by either a GT system or an autologic system, which every good BMW independant will have. Doing so will give you a more accurate indication to what the problem may be, as guess work may become expensive.

I think I may have to go to BMW I have a feeling it may be the MAF but not sure how to test. I have cleared the code and will now try tomorrrow with MAF disconnected. The rough idle is imtermittent and drives a treat. Will keep you updated on what happens Thank you for your prompt reply and very helpful appreciated John

Hi mate,

Yeah, unfortunately, when the MAF packs up- it doesn't always kick up an error code.

We see this all the time, only way to be sure that the MAF is at fault is to view the live data readings on a BMW specific scanner and see how that is operating.

but speaking from experience, a fuel trim fault code could be caused by a dodgey MAF sensor.

Disconnected MAF no problems so far so I think it is the MAF no faults showing so I think possibly a bit of luck here but assisted with the help of the members Abig thank you John

Hi John,

So, it seems it may well be the MAF then?

By the way, have you tried cleaning it at all..................most of the time, on beemers, if the MAF is buggered- its buggered but cleaning it with some carb spray may help but don't spray the can too close to the sensor wire it self as a strong jet may dislodge/break it.

Hi all I tried cleaning the MAF with Carb cleanner but it does'nt seem to have worked. I am now looking at a new MAF Any ideas where the best place to get one is. Been quoted £180 + vat

You could try www.eurocarparts.com or www.gsfcarparts.com.

If yours is the E39 series then I think they do a cheaper alternative part on eurocarparts at around £90 + vat

They are not BMW approved parts, but to be honest, they should be fine...

other options available to you are bmw breakers... you may be able to get one from a write off.. try these.. http://www.quarrybmwspares.co.uk/... drop them an e-mail, they may even offer a warranty on the part if you are lucky which is of course beneficial...

hope this helps...

mightybmw

Hi everyone
You have all been very helpful and I was convinced it was the MAF. I had arranged to get the LPG put in but delayed due to not running properly. They LPG people said they would look at and I agreed. They put the car and put on computer. They also thought it was MAF until they noticed some oil aroung the rocker cover. Took off the oil filler cap and tested suction so now looks like possibly a blocked suction pipe.Blew a lot of smoke out scared the life out of me thought engine had gone. So be ware it is very easy to think MAF and I was convinced. Be sure to check this out could save you a lot of cash. Car getting LPG put in as we speak so will keep you updated. This is a brilliant site and I have only recently joined. Keep the posts going, a good site and very helpful members. Thank you John

Thanks very much for your input john... Its great for us to get the feedback like this and a resolve to problems posted... Its often difficult for us behind a keyboard to diagnose problems without looking at the car, we do our best, but its people like you that make websites like these extremely useful...

Thanks...
Mightybmw.

Hi all would appear to be a crank case breather new one BMW supplied £40. Think the give away sign was the suction and oil weeping from the rocker cover. So worth giving a check first. Quality oil and regular oil changes can assist in preventing but the mechanic mentioned Castrol oil. Does anyone know what he is talking about? Regards John

I think what all he is saying, that cheaper oil isnt as good as the expensive stuff... And to some extent he has a point but isnt necessarily the be all and end all...

There is a website somewhere, i will try and dig it out for you, where they run comparisons with all the top brands, they did a test against metal that simulated an engine and it threw up a few surprises!... Some of the expensive oils actually wasnt as good as the average oils on the market, i think the test proved that an oil brand called royal purple provided the best protection for the engine, with minimal clogging, so to speak...

However, i dont see the oil damaging the rocker seal or breather pipes, if the rocker covers are leaking then thats because the sealant or the rubber gasket has just gone old and failed, pretty much every engine will suffer this through its operational life... generally speaking the rubber or sealant just lose effiency, then fail.

Personally i would recommend spending an extra £10-20 on a 5 litre bottle of good quality semi-synthetic oil, over lets say, an asda own brand oil.

Hi all
Got LPG put in and is running sweet New rocker cover breather put in and its like a new car, incidentially I have had BMW die hards drive the car and cannot believe how good the LPG is. They were all very impressed. You can not tell the difference maybe slightly and just slightly less power. But it is a 530i and wouldnt think a slight drop in power would make much. I really would not know when on LPG or Petrol butI suppose the technical aspect of it would suggest it will be a difference due to a less octane. But if you have any questions please don't hesitate to ask I think I will start a new TOPIC under the lpg HEADING so anyone interested can ask me questions. Just wanted to update you as I had mentioned it and wanted to keep you all informed

Great idea jonno... my knowledge of lpg is slim to say the least, and it would be great for members to comment..

I do believe LPG will become a large industry when the petrol prices rise again..(which they are doing right now )... So, first hand knowledge and experience with it, would be a great addition to the forum!

Nice one!

Many Thanks,
Mightybmw