946 spider has me completely stumped
I have a 2009 2.4 spider and it's developed some real problems. Last week I got a warning saying that the DPF filter was blocked, but I drove on a long run from Hereford to Manchester and back, and it disappeared. Then, on my way to work last Saturday it went into limp mode, and every time I restarted it would clear but come back within around half a mile. It did the same on the way home, and then it finally stalled about half a mile from home. I managed to start it and just about it limp it , but it didn't sound good and had no guts whatsoever. I read a few forums and the advice seemed to be that it was either a low powered battery, a dirty EGR or a blocked DPF filter.
So, I got a new battery and I cleaned out the EGR, but neither made any difference. Now though it won't start at all. After maybe 12-15 attempts it will cough to life for about a minute but then stall again, but when it does run it sounds really rough and it blows out a LOT of white smoke. We've plugged in a diagnostics jobber, but all that's on there is the DPF warning. This clears but then comes up again when you finally get it to run briefly. I rang a local garage but they said whatever the problem is, it isn't the filter. Does anyone have any experience with this or know what the cause may be? Thank you in advance for any help, and sorry for the essay!
By the way, it's not down to me putting petrol in, and a mechanic mate is confident the head gasket hasn't gone.