Ford Fiesta 2014 petrol - Fiesta 1.25 petrol misfire reoccurring

Honest John Back Room » Technical matters
View Threaded
Wed 13 Jan 2021 13:14
Ford Fiesta 2014 petrol - Fiesta 1.25 petrol misfire reoccurring - Lukas Stapleton

Hi,

Had a misfire on cylinder 3 and changed spark plugs, coil pack and HT leads.

Fault disappeared and keep reoccurring and dissapearing.

I am at a loss on what the issue now is?

Can only imagine it is a compression issue or fault clearing issue as couldn't clear the fault?

Any help and advice will be much appreciated.

Thank you.

Reply | Report as offensive | Link
Wed 13 Jan 2021 13:31
Ford Fiesta 2014 petrol - Fiesta 1.25 petrol misfire reoccurring - craig-pd130

Is the problem always on #3 cylinder? Is that what the codes always say?

I wonder if the MAF is dirty and needs a clean, or there's a vacuum leak somewhere on the inlet side (a split hose or similar).

Reply | Report as offensive | Link
Wed 13 Jan 2021 14:03
Ford Fiesta 2014 petrol - Fiesta 1.25 petrol misfire reoccurring - jc2
Injector?
Reply | Report as offensive | Link
Wed 13 Jan 2021 21:13
Ford Fiesta 2014 petrol - Fiesta 1.25 petrol misfire reoccurring - Lukas Stapleton

If it was an injector would you expect rough running and poor fuel consumption?

I have none of this runs as it normally does

Reply | Report as offensive | Link
Wed 13 Jan 2021 21:11
Ford Fiesta 2014 petrol - Fiesta 1.25 petrol misfire reoccurring - Lukas Stapleton

Yes always goes back to cylinder 3.

I will check for any split hoses or dirty MAF sensor.

Thanks

Reply | Report as offensive | Link
Wed 13 Jan 2021 21:22
Ford Fiesta 2014 petrol - Fiesta 1.25 petrol misfire reoccurring - elekie&a/c doctor

what oil are you using, and have you done a compression test? A dirty maf wont give a misfire on one cylinder. Modern maf sensors are digital thick film devices, there is nothing to clean.

Edited by elekie&a/c doctor on 13/01/2021 at 21:59

Reply | Report as offensive | Link
Thu 14 Jan 2021 08:42
Ford Fiesta 2014 petrol - Fiesta 1.25 petrol misfire reoccurring - craig-pd130

Modern maf sensors are digital thick film devices, there is nothing to clean.

Genuinely curious about this - I recently removed and cleaned the Bosch MAF sensor on our Corsa E 1.4 petrol. The two little wires which are joined with a blob of plastic had dust and grime on them, a few squirts of electrical cleaner rinsed the grime off and left them shiny. On replacement, the hesitation just off idle that had been annoying me had gone and hasn't returned.

Reply | Report as offensive | Link
Thu 14 Jan 2021 09:35
Ford Fiesta 2014 petrol - Fiesta 1.25 petrol misfire reoccurring - Lukas Stapleton

That's interesting going to take a look at mine see its condition.

As misfire is to the same cylinder each time must be something simple but not obvious as it seems.

Reply | Report as offensive | Link
Thu 14 Jan 2021 09:33
Ford Fiesta 2014 petrol - Fiesta 1.25 petrol misfire reoccurring - Lukas Stapleton

I am using oil as per recommendations from Ford.

Not done a compression test as of yet. Do you know what the compression readings need to be on this engine please?

Reply | Report as offensive | Link
Thu 14 Jan 2021 10:46
Ford Fiesta 2014 petrol - Fiesta 1.25 petrol misfire reoccurring - skidpan

Fiestas with this engine as far as I am aware use wasted spark ignition (unless later ones are fitted with coil on plug but since the OP quotes replacing the coil pack that seems to be unlikely). Plugs fire in pairs and if one misfires so does its partner.

Having replaced all those parts it can only be something deeper in the engine.

Reply | Report as offensive | Link