Hi. 

I'm new to the forum and I hope I'm doing it right. 

I got problem with my wife's car. Fiesta MK7 1.25 petrol. On cold start revs are erratic, jump up and down, sometimes it feels like it's about to stall, it stabilise after a while but they stay high longer than they used to did. As soon as the engine reaches it's temperature the revs are stable and stay below 1000, also it starts normal every time.

I already cleaned throttle body, checked pipes connections, cleaned manifold temperature sensor, tested battery and disconnected for 15 min, started engine until warm, turned off and started again. No improvement.

Anything else I can do before taking it to the garage ?

Any help much appreciated.

Check for a minor vacuum leak, also how old are your spark plugs?

Thank you.

Sparks done last summer, full service done every year May. What's the best way to look for leaks? 

Update.

Picked it up from a garage, 🤦‍♂️ mechanic said he couldn't find any faults but he cleaned body throttle for me ( I cleaned it already week earlier) and I should give it a try. Obviously nothing changed.

My question is, if the revs stay relatively high 1000-1100  until engine is fully warm, could it be temperature sensor or something? There's no MAF on this model.

Any help much appreciated. 

 

Hi Ive got the same prob with my 2016 1.25 Fiesta.The engine does not cut out and once at normal temp stabilises which is usually 5 mins.Seems to reach operating temp very quickly but doesnt overheat 87k on the clock.

Try this, turn key to run, wait 30 seconds, start engine.

The fuel system needs more time to stabilize. I did this on my 14 Focus, and it worked with the high to lower rpm's transitions.   

Best wishes 

I have since noticed this only happens when its really cold .

Possibly a dud coolant temperature sensor. Plug a fault code reader in and see what temperature it's showing from cold. Should be low single figures in this weather, if it's showing much higher then its a dud and telling the ecu it's already warmed up when it isn't.