I've had problems with my 1.9 tdi Roomster, 2010.

Occasional poor starting, missing and stalling at low revs, reduced fuel consumption,

I had someone read error codes and they related to electrical problems with intake motor flap. turbo wastegate solenoid, EGR vac solenoid, camshaft sensor and speed sensor. I decided the best place to start was with the cam sensor, bought one (should have checked first), and when I checked the feed there was no voltage.

Now I'm not sure where to turn, there is very little information on the net. I suspect a relay, but they are almost impossible to get at, and I don't know which one may be at fault. Can anyone help?

Have you checked fuse 28 (10 Amp rated)?

Yes, all fuses OK

Do you happen to know whether your 1.9 is engine code BSW, or BLS?

Both were available from May 2009 on, but have different wiring in places.

I will try to find out tomorrow, thanks

Some info on where to find it here: Engine code and why it's useful to know - Handy Topics & Guides - BRISKODA

It's a BSW engine code

OK, well cam sensor and charge pressure and EGR solenoid valves are all fed from that fuse 28 10-amper on blue/black wires, so check that the fuse isn't loose, and doesn't have corrosion on its contact blades.

Also check your air pipework coming towards engine from airbox.

Wiring diagrams show a heater element N79 described as "Optional equipement" [sic] which is a little heater element to prevent freezing of a breather pathway, I believe. These have been known to cause partial or full short circuits. If you find a 2-way connector with blue/black and brown wires, in that area, disconnect it and see if that restores feeds to other items.

Take a photo of the location if unsure.

Edited 4 February4 Feb by Breezy_Pete

So the first thing I did was check that fuse. It was good then and still is. However it was in the wrong slot. I'm trying to think of a scenario where I'm not to blame but the facts seem to refute the possibility. It was the cam sensor after all, and even my poor reader managed to erase the codes and remove the error lights. Thank you very much for your help. I will be posting again soon on another issue so don't go too far....