Over revving when changing down gear

Could be idle air control valve sticking , needing cleaned or replaced . Or this similar complaint from another site might help .


Question
Ford Fiesta Finesse 1.3 hatchback - year 2000 (Mileage 59000)

I have a problem with erratic idling. When driving normally the car runs smoothly. However when approaching the lights, particularly in hot weather with a hot engine, or when in heavy traffic when coming to the idling position the car suffers from erratic "idling / surging" for a few moments with highish revs and then settles down to idling normally. If I press the gas pedal it does the same and returns to normal after 10 seconds or so. I have replaced the catalyser, the throttle housing unit, fuel filter and the lambda sensor. But the car still has the same problem.

Can you suggest a course of action?. I am at a what do do look for next.
Submitted: 361 days and 20 hours ago.
Category: UK Ford Value: £11 Status: CLOSED
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Accepted Answer
Hi

There are a number of things this could be, I would recommend having the Engine Management Fault Memory tested. This may point straight to the fault and save you time and money in the long run.



There are two common problems with this model that may cause your symptoms; one is the throttle position sensor. This may or may not show up on a Diagnostic Test, but be careful sometimes it's the sensor sometimes it's the wiring.



If no faults are recorded on the Diagnostic Test I would look to cleaning the Idle Air Control Valve, provided it has a separate one and not one built into the throttle body. The IAC Valve tend to get gummed up with Carbon from the Breather System, this causes them to stick and may cause your symptoms. Cleaning the IAC Valve is usually a temporary fix so if the fault returns you may need to replace the Valve with a new one.



I hope this is clear, if not let me know and I will try and explain it better



Many Thanks, Ted

Expert: Ted Wood
Pos. Feedback: 100.0 %
Accepts: 14
Answered: 7/6/2009
Ford Technician

City & Giulds of London Institute Qualified Tecnician, Ford Main Dealer Experienced



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