Engine wont rev, no power lots of smoke

Hi, I hope someone will be able to help me. I have a serious problem with my Golf 5 1.9 TDI (1K5024 BLS).

The car broke down and needed to be recovered. After recovery it does start but wont rev above 1500rpm and produces huge quantities of smoke from the exhaust.

I have looked all over the engine and cannot see anything obvious. I have also removed the intake flap and EGR valve, both were cleaned and the EGR was checked for operation by connecting directly to a battery. I looked at all of the hoses and vacuum lines and cannot see any leaks / spits. This was put back together, however the car is just the same and struggles to even get to 20mph.

A diagnostic scan only shows code P0698 voltage C low, however that code has been there for a few months with no noticeable problems.

Also a few months ago a scan showed 3 of the 4 glow plugs were faulty so all were changed. The car was okay before and after the glow plug change.


I really need tome help to identify what the problem is.

Thanks in advance for any help you can give me.

Regards

Engine wont rev, no power lots of smoke