Hi,

i have been reading about this thread which I am having same issue as mine 530d with M57N also fluctuate at 1200rpm. I was thinking maybe high pressure fuel pump regulator or may be one of injectors is playing up. I did check with ISTA and INPA as well and all the injectors seems to work fine.
hope someone will reply on this thread.
also I did check the module of fuel pump which is absolutely fine.

 

Do you notice a difference from when the a/c is on/off

 

thanks for the quick message mate.
no I never thought about it. I will give it a go and if while a/c is on and fluctuations goes then a/c off and fluctuations back what does that means?
thanks

 

It's an electrical/power issue you have to find. Either Alternator, compressor, battery issue. It's pulling more power than something can handle

 

mate I’ve done lots of things to be honest In last month
changed glow plugs and control unit
both thermostats
alternator
new battery
gearbox service
I am thinking about high pressure fuel pump regulator 🙂.
any thoughts please??

 

Have you serviced the gearbox? Have you tested your pump? Sadly, when you get fluctuation it's a prices of elimination. Do you have ista and INPA

 

I know what you mean 😞. But I don’t wanna let her go,I know she’s 16 years old now. Yeah I did service the gearbox with genuine ZF parts and I do have ISTA and INPA.
Have you got any ideas hence asking about ISTA and INPA mate?
Thanks a lot

 

You shouldn't have and codes. I've know the map sensor, pump, alternator, battery or gearbox solve this issue. But have heard of other sensors solving RPM fluctuation issues.