Hi there. I am new here and don’t understand exactly what’s going on haha. Bear with me.

so I need to pick your brains. I have a 1.25 16v Petrol Mk4 Fiesta. X reg from year 2000.

it has been a dream until last few days. The weather was hot so I stuck the a/c on and it didn’t work. Was blowing hot air. Then my car starts to idle erratically, fluctuating between 1300-2600 rpm with no gas being fed. At first this would happen every time I stopped the vehicle, the revs would do their grr-grr-grr noise at lights or whatever.

The most commonly suggested issue online was to check all the hoses for a vacuum leak, which I have done to the best of my limited ability. I have used lighter fluid on a cold engine to check for leaks at all pipes and nothing increases the rpms at all. I have taken off and refitted the air intake box and changed the air filter. I have also changed the cabin filter just in case. I did find a tiny hole in the hose which runs from the top of the PCV and I taped that up and this made no difference either, although it will need replacing, it’s a bit difficult due to the fact the bolt holding the clip is behind the radiator.

I have researched the topic on here and seemed to be most commonly a problems with the idle control valve, TPS or another sensor. I have cleaned the idle control fully and it made no difference, I then changed the TPS for a genuine part and no difference. It is not happening as much but it’s still happened every time it is started - and sometimes during the journey but much less.

I am constantly getting hot air from the vents - with the blower off and this is also accompanied by the main engine fan constantly turning too. I don’t know what else to try now as the car runs smoothly and perfectly apart from this new over revving thing at idle.

Any help massively and greatly appreciated!