Buzzard88 wrote: ↑Wed Apr 10, 2019 12:42 am
AndyBeech wrote: ↑Tue Apr 09, 2019 7:49 pm
When you disconnect the MAF the car reverts to the Alpha-N map, which I believe estimates air volume instead using the engine speed and TPS. Do some Googling on it but IMO disconnecting the MAF doesn't prove anything conclusive as it doesn't really help you narrow down if a sensor is giving you an issue as the mapping has changed.
Have you tried INPA / DIS yet, see if you can run some tests and check for error codes. I fear your going to end up replacing a lot of expensive parts for no reason. For example, the ICV replacement is pointless, it really just works or doesn't it's a simple valve that opens and closes as you would have seen. Cleaning it is good but I wouldn't waste money replacing it.
It's safe to run without the MAF connected but absolutely no reason to do so long term unless you've specifically had Alpha N tuned for your modifications, such as running a CSL airbox where you have no MAF for example.
Oh, INPA would be useful for checking your long term trim's/adaptations, see if there's anything untoward there
An interesting option to maybe get an Alpha-N map tune. So do you know if the closed loop mode is running with the Alpha-N map, the same Alpha-N map as when the MAF sensor is disconnected?
I Have not yet tried INPA or DIS as I am still waiting on my cable to be delivered, but very keen to do so.
Well I wouldn't go the Alpha N route personally, unless you've got specific mods that require it and can take advantage, not a cheap route either. Alpha N doesn't adjust fuel trims to compensate for normal engine/sensor wear. It just runs best case scenario as its tuned to the optimal workings of the parts/engine whereas the base map will compensate for readings that variate from the factory defaults to achieve (I believe) lamba 1 or as close as. As a road car, the base map is fine but it does come with it's quirks, especially on for some reason our DME for the S54 which is slightly different to the M3 variation. I'm not sure anyone has worked out exactly why this is because the problem is fairly common as demonstrated on this thread. Alpha N still utilises the lamba sensors as normal as far as I am aware.
Sadly, trying to fix it can also be a money pit as there usually is no obvious reason, fault codes or otherwise. It could be many things related across the whole intake/fuelling chain.
All the sensors/working parts along this chain could be causing the issue, but probably the most important are:
VANOS
MAF
Lamba sensors
Air leaks/split pipes/cylinder issues (including head gasket)
TPS (including throttle pedal)
Throttle Actuator
Fuel system (including injectors/filter (which you can't replace)
Cam timing
CATS
Cam sensors
There's more but you'd hope you would get a error code for failures, though as mentioned, the base map will compensate for sensors not giving expected values within pre-programmed variations without giving error codes but potentially small issues with performance. As mentioned, the DME is looking to achieve lambda 1 and will adapt fuel trims across it programmed tables, long term and short to achieve this. If the lambda sensors (usually pre cat) are off, which is quite common on the S54 because of wear on these sensors then it messes up the whole chain to a degree so if you haven't already, deffo look at replacing the pre cat sensors.
After that, it becomes tricky. The VANOS controls the cam timing constantly (and as such the A/F ratio) and this in itself works by the readings from other sensors so it can be directly wrongly controlled by 'off' sensor readings or not adjusting correctly to correct sensor readings if its slightly faulty but not enough to give an error code. It's a proper minefield as one thing usually dictates another along the chain and our DME generally won't give error codes for these 'minor' faults as they aren't severe enough to warrant it with it's inbuilt 'ok' deviations.
Sorry if a lot of that doesn't actually help but hopefully it gives you a bit of an idea as to the confusing nature of the issue. If I was you, I would clean what you can which it sounds like you've done. Get the intake plenum off and clean the TB's, look for split hoses, ICV etc.
Then your looking at replacing parts, the obvious one's:
MAF
Lambda's
VANOS system
Check cam timing (can easily be disturbed and you want someone competent to check it/set it, will be done with any VANOS work so 2 birds with one stone)
Get it plugged in at BMW, there is a software update for our DME's and it may not have been updated. It was some time ago the update was released but mine only updated when I asked about it at BMW in 2016. It mostly addressed cold running issues but still worth doing.
After that, as you've already experienced, your into replacing parts which may or may not be fine, and on these engines, it's not a cheap venture, especially when you might be replacing parts which are perfectly fine.
It's a tricky one with no definitive answer sadly. Aim for the bigger/preventive parts that will benefit the resale value if you can otherwise you could be spending a lot of cash without benefit or perceived benefit when you come to sell. For example, a refurbished VANOS might help and it will also be a good thing for the future if you see what I mean as worthwhile preventative maintenance.
To add, when you get DIS working, do the VANOS test and see what the readings come back as. It will give a +/- 5 variations to factory defaults and if you are a fair bit outside these it could indicate a problem there, and wouldn't necessarily give an error code either.