The history is actually a bit more complicated than I first let on. Perhaps I should explain.....
Beginning of this year, whilst doing a track day, the fan came on constantly. I was told by a mechanic it was on 'Limp home' mode but after doing some tests he couldn't work out why. On my way home I got five miles down the road and it stopped - problem solved.
Shortly afterwards I started getting a ticking sound from the engine bay. Cracked manifold. I didn't have the time or money to fix it so drove around with it broken for 6 months :shock: Over that period the fan thing happened more and more often till a few weeks ago it came on constantly and hasn't gone off since. Shortly afterwards the Engine Management Light came on and shortly after that I started to experience slight running problems.
Something made me think now was the time to get the manifold replaced so I booked it in with the dealer. They told me one of the studs has sheared off in the head. I couldn't afford to have the bodywork removed and the stud drilled out etc. so I got them to put it on minus one stud. They read the ECU and got P0170, P1133 and P1171.
So the situation now is that the manifold is on minus one bolt, the EML is off and has stayed off, the engine idles slightly low and lumpy, I get a misfire when slowly accelerating from <2000rpm, a similar misfire when coming off the accelerator, the fan is on constantly and the tips of the exhaust pipes are blackened. I've driven it around and had the ECU checked again but codes came up.
The theory I have developed now is that the loss of air through the crack in the manifold caused sensors to misread and result in incorrect (Rich) fuelling. The manifold was replaced which stopped the majority of air loss but in the 6 month period of driving around with it broken the deposits left by rich fuelling have buggered up the Lambdas so it's still running rich.
Sound plausable?