Ford Fiesta 1.3 not idling

[Pierre 11]

Hi all I have a ford fiesta mk5 and it's not holding the idling revs. I changed the throttle body but after one month the problem returned.

There is no check engine light on.

What could be the issue pls

Thank you

 

[scotman]

Check vacuum hoses and their connections. Also might want to have a look at the idle air controls. Did you swap over the existing IAC valve to the new throttle body? That would be where I would start.

 

[Handy Andy]

+1 per what @scotman said.

Best to keep the older throttle body - even if there is a core charge.

Many times - the "poor idle" can also mean broken vacuum hoses or a poor seal that is leaking, causing surges in the idle speed and if too much air, it might try to idle up but will not hold that speed knowing it's got an air leak.

It should also have a gasket or if not one supplied, you should put a new one in when you install the new throttle body.

So even electrical connections to the throttle body, if this problem has returned like you said it has, might also mean the electrical connector to it, is faulty, as to connections and to the wiring failure - like a broken wire or a poor ground.

This may also mean the MAF sensor (if it has one) on the snorkel might need cleaning or replacement - it's connector needs to be checked too.

There are two variants of the engine in that thing plus the fuel it can run, Diesel and Petrol - and Zetec motor or a Mondeo variant Endura - so there's a wide variety of things than we can talk about, but to help you - what kind of fuel and motor does the MK5 have in it - a simple photo goes a long way here...

 

[Pierre 11]

Another thing when it rains the car starts to misfire. I have changed the coil pack 2 years ago and also the high tension leads. Do you have any idea why it does it? I don't drive through deep puddles

Thank you for your help

 

[Handy Andy]

This may be an electrical - as in what sensors are under the engine - including the CKP sensor that determines where TDC is off the Flywheel on the transmission side of the motor. Look for moisture and wetting of the engine signaling a leak in the bonnet, a leak that is dripping and corroding the wiring and affecting sensors.

IF the harness is corroding - then the wiring itself is costly to replace - a new harness, let alone the sensor at that spot.

Some ethanol fuels "gel" when they mix with water - making the vapor-atomization - difficult and plugs up the injectors and can foul out the plugs..