Engine intermittently missing

[Haddocksrock]

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?
It can be the odd miss here and there or occasionally it is a bad run of stuttering that eventually clears. No warning lights come up when this happens apart from the ignition light as the engine cuts in and out.
Any ideas?
Fuel pump? HT coils?

 

[Handy Andy]

Best to get a scan tool for yourself, I do.

It's not "codes" that you worry about when things like this are starting to crop up.

It means you should look into getting a simple scan tool - like ones at the Auto stores that are about $50 (or less) - it's well spent when you realize how valuable they become when you can't find codes, but you know something is wrong.

It's the I/M monitors that you can view - that can give clues to where to start looking - more effective if the battery is in good condition and there are good connections electrically - loose or poor connections can make the system think there's something more wrong than there really is - it may be a loose connector onto a pinched wire or corroded connections.

That's why I/M monitors work - they let you see general areas of operation the vehicle. The vehicle checks and performs diagnostics as part of the "run time" when you use the vehicle and the key is on. The system reports and holds sections "accountable" for actions above and beyond normal operation.

The I/M like EVAP, Electronic (Misfire) Catalyst and Engine will show "NOT READY" or "READY" - they can go "NOT READY" and not pass a code onto the DTC. Because it was a simple fault so it keeps tabs of the operation. A few start cycles and no recurrence of that same fault, it won't store a code but it may place the sub-system in a "Monitor loop" mode. You'd see it as a "Not Ready" - then you can research the issue of that sub-system further with your mechanic to help them narrow down these faults.

Let us know if this might be a better option for you - then it can help your family track down conditions in your other vehicles you own too - ODB scanners are universal so they fit most of today cars.

 

[Haddocksrock]

Best to get a scan tool for yourself, I do.

It's not "codes" that you worry about when things like this are starting to crop up.

It means you should look into getting a simple scan tool - like ones at the Auto stores that are about $50 (or less) - it's well spent when you realize how valuable they become when you can't find codes, but you know something is wrong.

It's the I/M monitors that you can view - that can give clues to where to start looking - more effective if the battery is in good condition and there are good connections electrically - loose or poor connections can make the system think there's something more wrong than there really is - it may be a loose connector onto a pinched wire or corroded connections.

That's why I/M monitors work - they let you see general areas of operation the vehicle. The vehicle checks and performs diagnostics as part of the "run time" when you use the vehicle and the key is on. The system reports and holds sections "accountable" for actions above and beyond normal operation.

The I/M like EVAP, Electronic (Misfire) Catalyst and Engine will show "NOT READY" or "READY" - they can go "NOT READY" and not pass a code onto the DTC. Because it was a simple fault so it keeps tabs of the operation. A few start cycles and no recurrence of that same fault, it won't store a code but it may place the sub-system in a "Monitor loop" mode. You'd see it as a "Not Ready" - then you can research the issue of that sub-system further with your mechanic to help them narrow down these faults.

Let us know if this might be a better option for you - then it can help your family track down conditions in your other vehicles you own too - ODB scanners are universal so they fit most of today cars.

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

 

[Handy Andy]

Well, if you can adjust tappets - welcome!

That's a story for later...

But, what I was refering to was a simple scan tool, like this

​

You just need to see your simple I/M so no need to spend a ton of money on something you only play with when the thing you install it on, is broken..

About $40 at Harbor Freight - Menards and others are similar.

 

[Haddocksrock]

Well, if you can adjust tappets - welcome!

That's a story for later...

But, what I was refering to was a simple scan tool, like this

View attachment 8865​

You just need to see your simple I/M so no need to spend a ton of money on something you only play with when the thing you install it on, is broken..

About $40 at Harbor Freight - Menards and others are similar.

Thanks found something similar here in the UK from Toolstation for £28'ish 👍

 

[Handy Andy]

Since the Daughter will probably be using the car, when these moments happen - remind her to be alert to changes and remind her to use that device to look into events as they occur during the drive.

Don't shut off the car when she wants to check it - leave it running so she can see "live data results" if she feels the issues around those mis-fires it will affect performance.

Or, at least, have her contact you and if these events get severe, then you can have her drive to a safe spot and see about using that device to find those faults.

OR...

If she lives at home still, have you go out there (in the driveway) when she comes home to capture that freeze data for yourself - just don't shut off the motor so you can review that data and the I/M monitors before they get cleared when the engine gets restarted.

After the Fact:

You can also review this thread...
https://www.fordfiesta.org/threads/...-light-appears-and-rough-idle.8369/post-21568

 

[Haddocksrock]

Since the Daughter will probably be using the car, when these moments happen - remind her to be alert to changes and remind her to use that device to look into events as they occur during the drive.

Don't shut off the car when she wants to check it - leave it running so she can see "live data results" if she feels the issues around those mis-fires it will affect performance.

Or, at least, have her contact you and if these events get severe, then you can have her drive to a safe spot and see about using that device to find those faults.

OR...

If she lives at home still, have you go out there (in the driveway) when she comes home to capture that freeze data for yourself - just don't shut off the motor so you can review that data and the I/M monitors before they get cleared when the engine gets restarted.

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!