The wifes 03 fiesta 1.3 duratec has developed an iritating intermittent fault.

If you start it and do 20 miles or so all is fine and it idles normally 900 rpm ish. If you key off and restart it, either straight away or after a bit it usually then idles at 1400 rpm.

When it starts idling at 1400 rpm it will also hang for a split second when you take your foot off so say your at 60mph and take your foot off the car returns to what feels like 10% throttle imediately then 0% half a second later.

after a good run it sometimes sits continuously switching between a 2000 rpm idle and a 1400rpm every 2 seconds.

the engine warning lamp doesn't come on when its misbehaving,

Any ideas what it could be, I have search the net but just find owners of cutting out KA's that need an idle control valve.

I unblocked the tank vent earlier in the year and it was fine for 6 months but now its doing again.

any ideas greatly appreciated

Have you cleaned the icv?

Also tps wiring is commen on ka's

Yes ICV cleaned, I will try a new tps, I did find this thread that sounds familia:

http://www.bba-reman.com/forums/Topic86929.aspx

I will get googling the TPS wiring common issues on KA's

the faults intermitent nature definately feels electrical,

I did read about this issue a while ago and I think there is a ford fix that involves replacing part of the loom. This is due to connectors to a part becoming "loose" causing problem. I cant remember what part it was but think it was the ICV.

On a similar note, The fiesta zetec engine has a common idling problem that sounds similar to yours, I have diagonosed this on my kit. There are rubber vac pipes to the PCV that split, but is very hard to see unless you are looking for them.

Solved it, there was a big hole in a vac pipe (top right in the pic). According to the haynes it plumbs from inlet manifold to a one way valve in the rocker cover via a sensor which in turn adjusts the fuel pressure accordingly.




runs spot on now



[Edited on 10/12/12 by bigbravedave]