Fiesta 1.3 w reg idle running uneven when i start the car it ok but after about 10 mins judders badly when slowing down in low gear the eng revs are up and down

Is it possible the clutch pedal is interfering with the throttle? Start the engine in neutral and allow it to idle. Press only the clutch pedal down and see if this increase the engine speed. If it does speed up the engine and slows back down when you release the clutch then somehow this operation is where your fault lies. If it doesn't alter the idle speed, then rev your engine and release the throttle to see if it returns to idle immediately. If it is slow to return to idle then your throttle cable could be sticking. This means when you change gear lifting off the throttle has little effect and depressing the clutch to change gear causes the engine to race as the throttle is still partially open.

Spark plugs won't cause this kind of problem. It sounds more like the oxygen sensor in the air intake is faulty. You may be lucky by just cleaning the connector from the sensor or cleaning the sensor itself. It may be contaminated with dust etc. Otherwise it will mean a new sensor. Very simply, the oxygen sensor tells the EFI system the best air/fuel ratio to set at different throttle settings.

Hi Kristopher, A shudder from the manual transmission is usually caused from a defective part in the clutch assembly. It could be caused by uneven wear of the pressure plate (clutch cover) or wear on the clutch plate boss (The center of the clutch plate with the springs or rubbers which absorb the torque when releasing the pedal) A shudder can be generated from a defective engine or gear box mount, worn CV joints or spiders or a loose bell housing. Start with the last suggestion and work backwards as the clutch replacement will require the most work. If the clutch assembly has been replaced recently, and the parts available are of the same quality we receive where I am, you will need to do the job over. Regards John

that is your idle air controll valve very easy fix

these vehicles are known for ignition coil failure. typical symptoms include: Misfire, power loss, vibrating engine, poor fuel consumption. If the vehicle's engine vibrates, it be misfiring. Is your chk engine light on???

It sounds very likely to be the ICV

It seems like fuel pump gear is in wrong position. You need to remove drive belt and turn pump gear 360 degrees. Before you do that, you should know that there is 3 marks: first on flywheel, when 1 and 4 pistons is on top, second at the end of the camshaft and third in fuel pump gear (16 mm bolt). If you never do that before, I suggest you to go to mechanic, otherwise, you can do seriuos damage, like folded valves. 

Here is the common cause of surges, stalls at stops, slow idle speed, erratic idle speed, rough idle and engine hesitation (and other problems), it is in most cases the idle speed control air-bypass valve and or throttle valve and upper intake, these area's get full of gunk and combustion residue over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake

valve bent or valve seats worn

hey, check your coolant level on your radiator, take note I said " radiator not coolant reservoir.

there could be low coolant level that causes it.