Ok,

I was fed up with the problem of my car having a bad idle.
I called the Ford hotline (Only for Ford mechanics) in The Netherlands and told them about this problem.

They told me it's the swirl flaps. The is a small hose on the right underneath your gas valve (or w/e it's called). If u close/block it and the idle'ing goes back to normal, your problem has been found.

One problem.... It's a 600 Euro problem. You need a complete intake system.


This problem is well know for the Mondeo 2 liter. just never thought about it before.

This used to be a problem on the older version of the Duratec 2.0 HE engine, but the inlet manifold on the engine in the Fiesta ST doesn't use this design.

If I'm not mistaken!

A dirty throttle body can also cause this, a lot cheaper to sort out too, whip it off and give it a clean