Hi just got fiesta out today and fired it up. Now its always had a idleing problem but its started to do my head in. Its fine if i unplug the iscv but has soon as its plugged back in it starts to have a bitch fit. I have put new gaskets on and been throughly cleaned out but never changed. I have turned the screw on the throttle body but no matter how far i do it it doesnt make a difference and its really annoying any suggestions? ?

 

Wot i mean is it doesnt idle at 750 more like 1200rpm

 

Clearly the ISCV is working and doing it's job, the problem is somethings telling it to open by the amount that is causing your fast idle. When you unplug ISCV you have a mechanical base idle so it can not drop below what it's set at.

I should think 750RPM is a bit low, what can happen is if the idle is to low ISCV will bring the revs up for compensation then when the revs drop again to base idle it brings then up and again and so the cycle goes on.

So it depends on what you mean when you have turned the screw, I.E have you tried decreasing or increasing?

If it's not then then you need to be looking at what info your ECU is seeing, I would first be looking at TPS calibration and if not this then the CTS.

Martin

 

Well i turned the screw in the throttle body and it didnt make any difference either way i turned it or how much by. Should u be able to notice a difference? wot it tends to do during drive is when i nail the car and stop at traffic lights it goes bizerk to just under 2000 revs and takes ages to drop maybe 10 mins why does it all go away when u unplug iscv

 

I would check TPS calibration, when you unplug ISCV valve the valve closes as it has no power and therefore the only air that can enter is via the butterfly valve, the screw on the t/b holds the throttle plate open by a tiny amount just so a little air can get through for the engine to substain an idle, if it was allowed to close totally (I.E if the screw was removed) the engine would not run, the more you tighten the screw the faster the idle will get, the ISCV can raise the idle above base idle but not below.

Martin

 

Well i turned the screw alk the way in but not till it wunt go any further. Because i dont realky no wot to do alk i do know is it dint make a difference to the revs but it was sort of hunting think it needs a proper setup

 

It may not be a base idle screw, if it is it should act as a rest for the throttle arm, but as you have confirmed the ISCV raises the revs it's deffo getting info to do this from somewhere as I say most likely the TPS.

Martin

 

Yeah well i have thought that am gonna take it to motorsport developments do u think they cud sort it and also do i need to worry about fueling now i have messed with the throttle body screw

 

Any one eles know

 

Yes you won't go wrong by taking it there, Stu is a member on this site as well (Stu @ Mdevelopments), the engine has management so this controls all fuelling etc electronically, so no adjusting the what is assumed to the the idle screw won't effect it.

Martin