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!

 

The heater valve wants changing for your heater fault - get a gen. Ford one the pattern parts are usually crap even though they are cheaper. it's easy to change, follow the heater pipes and there is a plastic valve with 2 pipes on and an electrical sensor.https://parts.vospers.com/genuine-fo...rol-valve.html

For the high idle its usually the pcv pipes split, which you know about. It could be the VSS (vehicle speed sensor) holding the revs on , disconnect the 3 pin plug on the speedo drive of the gearbox and see if fault carries on.

 

Thank you so much for replying!

ive been at it all bloody day and not got any closer.. in fact almost had a total failure. So the hose connected to the top of the PCV was indeed faulty, it was quite old and had heated up against something hot near the intake which had caused a hole in the pipe. I am going to replace this but have taped it up temporarily - thoroughly with electrical tape.

one question:- the pipe coming from the underside of the PCV as you look at it from the top of the engine - the thicker pipe - that was caked in oil so I shook it a bit to see where it was connected to and it came off in my hand. As though it was not connected to anything at all. However there is a rubber grommet (or what is left of it) attached to that end and I have NO IDEA where on earth the other end of this pipe is supposed to go to! I have not had any change since reassembly and the car is still running - albeit with the same problems. The Haynes manual does not show me where this end of the pipe should go back to?! Would you happen to know?

I have had the alternator off as it seemed to come from the left of that, but, even with that exposed I can’t see the end of the pipe. The natural shape of this hose seems to suggest it comes from the rear of the manifold but there is nothing obvious.. Is it possible this is the vacuum leak?? Although wouldn’t the car be stalling due to the leanness of the mixture?

with regards to the idle problem I am having I have seen a few people suggesting the VSS but I have no yet located it (I am trying to find the part by sight on the car)…. But this does seem to be the solution most often come across.

would unplugging the VSS leave me without speedo being functional?

sorry for the long essay type post but I just want my car to work and money is so tight!

thanks.

 

I have now disconnected the VSS and it seemed to work temporarily, the idle dropped and I didn’t get the idle revving and then all of a sudden it started again when I’d done 10 miles or so…
I also have an overheating issue now - it wasn’t there before I played with the PCV valve, could that be linked?

 

I say this with a hint of hesitation because I don’t want to curse myself, but, issue seems resolved.

I disconnected the battery having already disconnected the VSS and since that - the idle rev has now stopped!

I still have the heat coming through vents but this is likely the HCV and once the part arrives and is fitted that should be the answer to that aspect. But so far - so good.

thanks to GVK for the advice!