my ford fiesta 2004 make keeps cutting out when i turn engine on in cold weather have to rev engine for bout 5 minutes to warm engine up then the car works fine , have had fault code test and says catalic converter and speed sensor errors have been told those wont be causing the problem, what could be the problem ive had new spark plugs fitted didnt change anything , confused had loads of different answers from various people including crank shaft sensor , lumber sensor , petrol pump , help !!

Were the spark plugs gapped correctly. If not it could be the cause of your problems.

first thing that springs to mind would be ecu coolant temp sensor, cheap and easy fix, but tbh, needs to be properly tested/checked otherwise its just throwing money in hope.

you mentioned codes for cat and speed sensor, were those codes cleared and if so, did they come back up again or not.

few more details might help....such as what model, wether you notice any other problems once its running, if the engine light flashes up or not.

not sure about spark plugs need to ask my dad as he done them haha ,yea code were cleared and engine light came straight back on ,lights been on for months and had it cleared a few times and comes back on all the time , a zetec model

also once the cars warm and starts up its fine drives like normal once engine stays on

had to get break down people out other day as can normally get the car warm and rev engine for a bit then engine starts fine but this time tried the usual but got no revs or anything just wouldnt start at all

any idea of the actual code numbers

the po500 and po420

could still be that temp sensor, laymans terms, that sensor sets the choke for cold start

ill just look those codes up, back in a mo :)

ok

P0500 speed sensor

although i have never had a bad speed sensor cause starting problems, its not impossible...the fact the code keeps flagging, it needs to be tested.

P0420..cat system efficiency below threshold

this is most probably a problem with the oxygen senor, which may be causing an overfueling, so could be related to your problem.

need to add, codes are a clue, not a reason, so faults could lie elsewhere but causing these sensor to flag up....plus sensors themselves could be fine, maybe a wiring fault or ecu fault for eg.

has the engine light only been coming up since starting problem, or did this occur before [or after] problem started

the engine light came on and the problems started

right, definitely related then..

if you fancy a gamble, i would try changing the ecu coolant temp sensor, cost should be under £3o, its situated under the coil pack on right hand side of cylinder head, as you look from front..

this sensor could be working within its set parameters, which is why it doesnt flag its code up, but still fool the engine into believing the engine is warm, when its actually cold...this in turn could confuse the oxy sensor, which is why this code is coming up...

the speed sensor is the one throwing me..

ideally, you need to get somebody that can read and understand live data, that will show where the fault lies, but expect to be charged at least £40 before they even find the fault.

ok thanks ile give that a go , thanks for your advice

no worries, good luck

The cat code is probably the cause - not the cat itself, but one of the sensors is probably gone and its probably the post cat sensor, the values whilst the engine is cold are out, I'd hazard a guess that even when warm it's probably not pulling as well as it could do.

thanks , it usually seems to drive fine once engine is warm

would be unusual for a bad oxy sensor preventing car starting from cold, as these sensors dont even come into operation till engine has started and sensors are heated up..

if you or you know someone handy with a voltmeter, easy to test temp sensor..

from memory its a 2 wire sensor....white/brown wire

disconnect sensor...carry out resistence test on sensor.

cold engine should read approx 39000 ohms

hot engine about 2000 ohms

reconnect sensor, volt check with ignition on

brown wire is earth, 0 volts

white is signal wire, cold engine approx 3.5v, hot engine, approx 0.5v.

if as above, sensor itself is ok.

these figures are for 1.25 zetec, think all the fiesta zetecs will be same , but if you have different engine let me know and ill check

ok thanks i have a 1.4 fiesta zetec

figures are the same

been thinking about this [dont forget suggestion of checking plug gaps put up earlier]

those 2 codes are a strange combination, not come across this before.....making me think you might have an earth fault somewhere on the engine, its the only thing i can think of that makes sense of those 2 codes..

so if it was me, i'd check those gaps, test the temp sensor, check the earth wires [can look up where they are if your interested]...failing that, it would most likely need a full diagnostic from somebody that knows their way around live data...

ok thanks yea if you dont mind

will take a while, but what the hell....im bored

note to self.....

must get a life :)

The speed sensor is a common fault, either the sensor has gone or the ecu needs a firmware update. It's unlikely to be connected and isn't the cause of the fault but is stored as a code.

Isn't the pre-cat O2 sensor a 4 wire heated type on that engine? Either 1 or both sensors are faulty or the engine thinks its at temp before it is which is then kicking the O2 sensor into life which is then making it run lean and cutting out?

thanks every1 will have a look into things and see what happens