Fiesta 1.25 - Idle Rev Seeking

Tesla · 18 Dec 2009 at 22:27

Hi all,

The Mrs' Fiesta Mk5 1.25 is playing up a little. I am thinking idle control valve, any idea where this is found on this engine?

When the engine is cold it idles around 1k rpm but every 5-10seconds the revs drop to 500-700rpm, the car almost stalls but just recovers.

After the engine has warmed up it doesn't seem as bad if at all existent really.

This isn't an issue that has started occurring due to the recent cold however is slightly worse on a cold morning.

Any input appreicated.

Ta

Bennie-Mac · 18 Dec 2009 at 22:35

By any chance are your headlights on when this happens?

Tesla · 18 Dec 2009 at 22:38

Bennie-Mac said:
By any chance are your headlights on when this happens?

Not something I have noted but nor thought about. What's your line of thought and will try with and without headlights over the weekend.

Bennie-Mac · 18 Dec 2009 at 22:44

Headlights put more load on the engine and i assume the heating would be on due to the cold adding extra load, so it could just be a case of adjusting the idle speed to compensate. However this may mean your idle speed is higher when the car is warm.

Voltjunkie · 18 Dec 2009 at 22:55

Checking the ISCV would be a good call. MK4/5 idle issues are most commonly caused by that or one of the sensors. It's on the bottom right hand side of the engine (looking top down) and looks like (or is very similar to) this:

If you push it into the engine block to ground it you should be able to see the valve move when turning the ignition on. You'll also be able to see if it's full of gunk that's causing it issues.

Tesla · 24 Dec 2009 at 08:30

Right, with the headlights off the car idles at around 1k rpm, I suspect lower but the needle scale isn't great.

With the headlights on the idle is the same but every 5-10seconds the idle dips to around 750rpm.