feezerstchris

My fiesta runs like a bag of nails cold and keeps dying, but is fine when warm, anyone help me? bin told it might be the coolant temp sensor, also gives the odd jolt here and there at low revs when driving.

jayRS

sounds like a sensor problem.
change it over and see, or get it on a diagnostic machine, but that will prob cost more than the sensor.
btw its the one in the bottom of the inlet manifold so its a bit of a pig to get out, prob find it just as easy to pop the inlet off quick, but remember there is a collent pip on the bottom of the inlet too so dont yank it off

tabetha

If it was a sensor fault it would be faulty all the time not just when cold or when it felt like it.
Check your CO as it sounds too lean, needs to be around 2-2.5% CO.
I bet you will find it is lean like 0.5% or similar.
tabetha
ps you could always just mark the positon of screw and adjust yourself to see if it improves.

jayRS

so if the sensor is naff and telling the ecu its warm so its putting in less fuel when in fact the engines cold and needs more fuel,...... how can it not be a sensor... as the fault is always there and wont "go" till the engine gets to the running temp when it runs fine

nick series1

I would change the sensor before you fiddle around with the CO screw.

In my opinion the Coolant sensor is more likely to be the problematic one here - assuming your description of "Fine when warm" is always/mostly accurate.

Sorry Can't remember !! Do FRST's adjust the signal to the fuel injector based on the voltage across the Coolant temp sensor ??
ie. no cold start valve ??

jayRS

yeah, they dont have a cold start valve, it uses the info from the sensor to act as a "choke"