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There’s an immobiliser unless you have physically removed it and had it coded out

Yes, as it can cut ECU power this fuel pump etc

If there's an immobiliser problem there should be a fault code stored, you need to read them

Annoyingly the garage I went to didn’t give me the codes before they erased them. One was for the camshaft sensor which I’ve now replaced, still no better. Replaced the ignition coil as well which they recommended and still nothing. I’ve got a replacement ignition switch from my local VW parts supplier but have no clue how to fit it.
It’s now got a permanent engine light which I can’t clear with code “unknown c0300”. Anyone have an idea what this is?

I should add as well that after I replaced the ignition coil and new cam sensor, the revs would spike from 600-900 every 30 seconds or so. Thought that was odd, maybe just calibrating now there’s no vacuum leak? There’s a tiny tube coming off the new vacuum hose which is sucking in air. Should that have a bung on it? Covered it with my finger and engine revs dropped substantially

That vacuum hose should be connected to something - have you got a pic?

Ignition switch is a steering wheel off job, then you have to pull the spline off the rack too to access it - not too easy

You can test a new ignition switch without fitting it in any case with a screwdriver in the key slot on the new one with it plugged in

Ok here’s a couple pics, including close up of that little valve thing. Made a bit of progress, cleared the codes and light is now gone. Still had c0300 and the code for cam sensor came back, showing p0343. Looked this up and it gave me this:

Symptoms of a P0343 engine code may include:

Check Engine Light on
Bucking or Surging Dies out, but may restart if the problem is inconsistent
May run fine, until it is restarted; then will not restart

Typically the causes for this code are:

Open in the ground circuit to the camshaft position sensor
Open in the signal circuit between the camshaft position sensor and the PCM
Short to 5 volts in the signal circuit to the camshaft position sensor
Occasionally-Camshaft Position Sensor faulty – internally shorted to voltage

The symptoms are exactly what I’m having, so i guess I’ll have to work through the list of causes and/or take it to an auto electrician.
Still unsure as to what the other code is for.

That should have a bung on it. Should’ve been one on the old hose

Ah ok, looks like I’ll have to find something to go on there then. Thought the brake pedal didn’t seem to feel any better

If youre saying that you can crank the engine from the key, and it seems like its about to start before it cuts out, I have a feeling it might be a faulty immobiliser or connection. You can check by removing the trims and plastics below steering wheel and above driver footwell, theyre held with torx screws. Its a small black box with 2 plugs going into it.
I had a problem like this - my car wouldnt start and I checked everything until realising immobiliser was completely disconnected. Another symptom of this was the fact that no OBD scanner would connect, it would always show Linking Error. You dont have this problem, but you do have a strange error code. Its worth checking though.

If you still have the cam sensor code, it might be worth checking the engine timing and the wiring and connection to the sensor.

Thanks for the additional suggestions.
I’ve just had the bumper off and cleaned up all of the grounding wires I could see which followed the cable to the cam position sensor. Checked the sensor wires for voltage and also ground and they were reading 0 ground 11.2v for middle pin and 4.7v for right pin (assuming those numbers are good). Cleaned everything up with contact cleaner and brushed off the corrosion with a wire brush. Made a little bing for the brake vacuum hose and reassembled. Started up first time and has been running good for a few minutes. Only a test drive will tell me if it’s fixed or not. I’ve not noticed this before but when I was in the engine bay and switched the key to on position the throttle body made a high pitched sound for 30-40 seconds and then stopped, is that normal??

Keep us updated, and I think the sound is normal mate but I could be wrong. I remember mine doing that, at least. It might be something to do with throttle body alignment after you take battery out

That TB noise is perfectly normal Its aligning itself

Thanks guys, I can stop worrying about that then I didn’t get a chance to take it out after work this evening but on Sunday I took it on a 30 mile round trip and ran fine the whole time (would have cut out a number of times before) I stopped to turn off the engine a few times too and started absolutely fine so hoping that a new cam sensor and clean ground points has fixed this

Sounds like its probably resolved. Glad to hear it

Took it for another drive today and was excellent, seems to have got a bit of power back as well (guess it’s because it’s sparkign the fuel/air mix at the optimum time now). Thanks for all your help, that’s another polo avoided the scrappy XD