2007 Passat TDI high idle, stalls, does restart.

I've been having troubles with my 2007 B6 Passat with a 2.0 PPD170 (BMR engine)

At first the problem presented with an intermittent stumble accompanied by a puff of white smoke. It would clear up then the car would drive normally.

I fitted a new ASV, because of an intermittent rough shutdown. The rough shutdown problem is fixed, the stumble disappeared for a while but is back.

Last time I went to use the car, just after I left my driveway I got a "Low oil pressure" warning. The warning and accompanying beeps only popped up briefly then disappeared. I pulled over and shut off immediately. After checking the oil level I restarted, reversed 100ft to my driveway and turned off, no extra noises/vibrations observed. It was left sitting after this for 2 days.

Today I went to move the car onto flat ground, planning to replace the hex drive key for the oil pump and the oil/filter. The engine stalled as I was moving the car. It restarted straight away but the idle speed was high, floating around 900, then up to 1000rpm (normally 800). A few seconds later it stalled again. Both times the engine stalled, there were no extra lights showing on the dash (the battery one came back on once it stalled, no immobilizer light)

What I have done:
I scanned the car with VCDS and I have no Fault codes for the Engine and Transmission.
I can hear the lift pump running when the ignition is turned on. (I have replaced the lift pump and the fuse for it ~75000km ago)
I did the timing belt/waterpump 11,000km ago, all 3 indexing tools can be inserted (DOHC) Torsion value is +1.5.
I still plan to go ahead with pulling the sump off and replacing the oil pump hex key.

I don't think it would stall from low oil pressure? and the warning for that hasn't appeared again, but I haven't run the engine for long. Avoiding doing that.

Help please, any suggestions?
Thanks

How is your EGR? Clean? Not sticking open?

Thanks for your reply.


I have almost got the sump off, once I have that sorted and re-assembled I will look at the EGR Valve.

Oil pump drive key removed, it was stuck in the balance shaft, turned the oil pump slightly then it was able to slide out. Hopefully no catastrophic damage but I have my doubts.


The new one slid in easily once I turned the pump to line it up, has a little play but doesn't feel excessive.

I have replaced the drive key, oil filter and filled up with new oil.

I turned the engine by hand and it feels good, I can turn it with a fairly short lever(then fighting the compression), same as when I did the timing belt.

Since I was confident it should now have oil pressure I started it up and its running fine? Idles normal, no stalls or problems yet. No bad or new noises. The engine sounds much better starting from cold. (having oil pressure probably helps, funny that)