My daughter's 2016 1.2 Fiesta has started missing at odd times. I have put in new plugs but no change. Local garage has had it in but no fault codes showed up and no fault occurred on a test drive?

Can be the odd miss here and there or occasionally a bad run of stuttering that eventually clears.

Any ideas?

Fuel pump? HT coils?

I would suspect either the HT plug coils, or the spark plugs are poor quality/fake/counterfeit

You really need to use FORScan in order to read the Ford specific DTC's which will be logged. Most generic code readers will not show all the codes.

36 minutes ago, unofix said:

I would suspect either the HT plug coils, or the spark plugs are poor quality/fake/counterfeit

You really need to use FORScan in order to read the Ford specific DTC's which will be logged. Most generic code readers will not show all the codes.

Thanks for the reply. New plugs are NGK from a reputable source. The HT coil is the original part at 35k miles.

Local Ford dealers want an arm and a leg just to take a look unfortunately. I am almost tempted to just replace the HT coil and see what happens as I could buy 5 new coils just for the cost of the Ford dealer inspection!

It probably is the coils, but you could use FORScan (free) and check to see if there are any codes. You would of course need to buy a vLinker FS cable £33 but then you would always be able to do your own diagnostics.

FORScan: https://forscan.org/download.html

vLinker FS cable: https://www.amazon.co.uk/Vgate-vLinker-Adapter-FORScan-MS-CAN/dp/B0952P4MLP

33 minutes ago, unofix said:

It probably is the coils, but you could use FORScan (free) and check to see if there are any codes. You would of course need to buy a vLinker FS cable £33 but then you would always be able to do your own diagnostics.

FORScan: https://forscan.org/download.html

vLinker FS cable: https://www.amazon.co.uk/Vgate-vLinker-Adapter-FORScan-MS-CAN/dp/B0952P4MLP

Well you learn something new everyday! 👍

Thanks for that I might just do that although my mechanicing skillset dates from the days of adjusting tappets and climbing about in scrap yards lol

 

Just to finalise this for anybody, it pays to check the obvious!

Having replaced the sparkplugs I decided to move along the line of investigation. Checking the plug leads found 3 in perfect condition, the 4th was fine at the plug end but at the coil end it was covered with copper corrosion inside. On removing the lead from the coil it was so corroded that the metal sleeve had broken off and stayed attached to the pin in the coil socket. So that explained the intermittent connection and missing running.

New plug lead has solved the problem. Moral:- always examine the obvious and expect the unexpected!

4 hours ago, Haddocksrock said:

Just to finalise this for anybody, it pays to check the obvious!

Having replaced the sparkplugs I decided to move along the line of investigation. Checking the plug leads found 3 in perfect condition, the 4th was fine at the plug end but at the coil end it was covered with copper corrosion inside. On removing the lead from the coil it was so corroded that the metal sleeve had broken off and stayed attached to the pin in the coil socket. So that explained the intermittent connection and missing running.

New plug lead has solved the problem. Moral:- always examine the obvious and expect the unexpected!

Change all four

1 hour ago, DaveT70 said:

Change all four

Yes been changed as a set 👍