Idle unstable on Fiesta 1.25 Zetec
before i start, excuse me for my langage because english is not my first langage.
I have a problem with my Fiesta engine Zetec 1.25L 16V.
The idle is unstable.
when engine is cold idle is quite 1500 RPM. Less than 5 minutes later, idle drops at his normal value around 900RPM.
Sometimes, idle drops around 500RPM few seconds. Idle make "yoyo" few second after go back original value.
Also, when engine is in idle RPM, when i push accelerator, engine has some difficult to get RPM. But i drive my car, i no problem except when i stop in RED light in crossway. I always afraid my engine stop.
At this time, i ever changed gasfilter, airfilter. I cleaned idle valve and box which is called "boitier papillon" in french. It's the box where air is pass functionnal on accelerator gate.
I supposed my problem comes from :
Lambda sensor or airflow sensor or idlevalve.
Thank you for your help,