Ho hum, a few months after replacing the inlet manifold gasket and just before its MOT, my car has now started acting rather oddly.
It's an X reg (2000) Fiesta, 1.3l Endura-E engine.
Recently the car has started behaving in a way that I'm not quite sure how to explain.
Once it's warmed up, when going to change gears, I'll find that the engine revs somewhat when I press the clutch (without pressing the acellerator), with no rev counter I'm not sure what it's revving to, but it seems to be gradually getting higher and more noticable.
The most confusing thing to me is that if I coast to a stop (no feet on pedals in neutral, or just with the clutch in) the revs will return to normal just as the car comes to rest.
Using the brakes has a similar effect, although pumping the brake when stopped makes the engine rev slightly, but I think that's normal.
I've considered a stuck butterfly valve, a dodgy sensor of some type, or an idle air control valve, or the ECU, or something completely different. Basically, I don't know where to start... (Although I have checked the acellerator cable isn't getting stuck)
I suppose going to the Ford garage to see if the diagnostics say anything would be a good start, but I'd rather not spend however much it'll cost just to plug my ECU into a box.