Fiat Punto Running badly Until Warm

[ToothbrushMan]

Just lately ive been having issues after starting the car from cold. never had this problem before.

it will start and for a few seconds maybe 10 at most run ok then it quickly begins on a downward spiral of stuttering some popping revs dropping to 500rpm then shooting back up. its like you to play around with the throttle pedal to coax her to keep running feathering it accordingly. if you rev it the revs will rise then stick for a second then slowly fall. it can drop and hunt then die completely too as the revs drop and drop. start it up again and it will run but erratically as before but over the course of 1 to 2 minutes she will eventually run on her own as the temp starts to rise..
.
I have already replaced what I thought it could be - the idle valve but no change.

i have not done any work on the car lately to suggest ive messed up anything.

what could it be, any checks to do?

Once the car is warm she idles and drives fine. yesterday though under similar conditions I started it from cold and it was fine so a lovely intermittent ignition/starting fault

[Nigel_O]

Sound like an air leak - check the intake hoses

Which engine?

[Mound Dawg]

Is it using water at all? I've found on a few occasions with an old 1.2 Mk1 Punto that if the head gasket's gone, water finds its way into a cylinder (usually no. 1) overnight and this drowns the plug so the car runs rough until this burns off.

[Dave Brand]

It MAY be a faulty lambda sensor. You need to get a diagnostic check done.