Urgent Help Needed!!! Idle speed... - Moby
Re: Mk4 Fiesta 1.3i Endura

A few days ago I noticed that when accelerating hard the idle speed rises dramatically during gear change. This is most pronounced when changing between between fourth and fifth gear.

I have replaced the ISCV with a brand new one (off another Fiesta of mine) but the problem persists.

Any help appreciated - I need to get this sorted ASAP, tomorrow if possible.

TIA
Moby.

Urgent Help Needed!!! Idle speed... - David Davies
The recommended cure for this problem is to renew the throttle potentiometer and the section of wiring loom which connects from this into the main harness.Apparently problems with this part of the wiring are sufficient for the engine ECU to think that the throttle is not fully closed and hence not to implement idle control.As a temporary fix for the problem it is a fairly common practice in the trade to disconnect the gearbox speed sensor.Doing this does stop the engine overspeeding but can cause an unexpected stall in some cases.
David Davies (Tune-Up Raglan)
Urgent Help Needed!!! Idle speed... - Moby
Thanks for your reply Dave.

How do I disconnect the gearbox speed sensor? It may sound like a silly question, but where is it?

I am actually back in S Wales this weekend and will need to get this thing fixed. If it is the throttle potentiometer/wiring loom how much would is this likely to cost?

Thanks for your help
Moby.
Urgent Help Needed!!! Idle speed... - David Davies
Speed sensor (known as VSS) is located on the differential housing at back of gearbox.Look for a three wire connector and the wire running vertically from it in the bulkhead area.I'd estimate about £100 to replace the previously mentioned parts.
David Davies (Tune-Up Raglan)
 

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