Ford Fiesta "stumbling" or "choking"

[peppera]

Ford Fiesta Finesse 1.3 petrol
2003
65k

When shifting between 2nd/3rd/4th (particularly on hills or when more throttle is being used) the engine will miss a beat, as if it's not getting enough fuel, air?

I have changed spark plugs, spark leads and used some fuel cleaner fluid in the tank.

Changed Air filter...still no joy.

Changed Fuel Filter too.

The engine seems to make repetitive "hisse" noise when idling from cold, but this clears up after running the engine for a few minutes.

Could it be the fuel injector not opening and closing correctly? Does anyone know if it is a single or multi injector? Pricey to replace or cheap?

 

[Belle427]

have you had a good listen under the bonnet for the hissing?
you could just have a split hose somewhere

 

[peppera]

I have had a listen, and it's seem more of a very quiet "tsk, tsk", but quite erratic.

If it was an air leak I would have thought it would happen every time I started the car, whether hot or cold, and wouldn't disappear after 5 minutes running?

 

[stuartturbo]

oddly had a simiular issue on my wife fiesta.
It was the 1.4 though.
On the front of the engine under to maniford
is a hose that links bore 1/2 to 3/4 with a tiny one way valve in mine had split and collapsed causing simiular issues.
hissed till warm.