I've had an issue with my E61 530d that I've been trying to track down for a while.
It's intermittent power loss and always sorts itsself out quickly. It's as though the turbo has no boost temporarily, yet a few seconds later, it's back strong and fine for a while.
I've replaced the MAP sensor and have ascertained that the VNT in the turbo moves freely and the electronic actuator has no obvious issues. I have an Ecotune DPF and Cat bypass and the associated remap (which is fantastic)
I've seen it mentioned a few times here to try disconnecting the MAF for fault diagnosis, so I've given that a go and can confirm that with my MAF unplugged:
The intermittent power loss seems to have gone completely
The slight cloud of fuel smoke I was getting over the last few hundred rpm of the rev range has cleared significantly
Power overall seems to be consistent, but slightly lower than I know it's potential is
mpg seems to have improved from high 30s to low 40s
So, is this as simple as meaning the MAF is knackered and needs replacing or is there more to it than that?
I'll be a happy man if this is sorted, it's the only niggle in an otherwise really smashing car
I don't know to be honest.
I just know on mine it's fine at idle, but if you apply any throttle and raise the revs a little you get this type of thing:
where the nominal and actual appear to be out of sync and the nominal value has a '!' next to it. Stan told me that can be due to a coked up head, so I was going to give the terraclean thingy a go @ Â£100 as a better alternative to removing the head
When you unplug the maf the engine management also closes the EGR valve permanently until it is replugged... Try removing the Vac hose from the egr valve and see if your issue persists. If it is resolved then we can simply arrange a tweak to your software so you have no EGR related EML... You're better off without it anyway