Engine fault caused (very likely) by Ford Dealership

Looking to get advice from anyone who's been in a similar situation - apologies for the long post ahead

 

Region: Northern england

Model: Ford focus ST LINE 1.0 mhev 2024

Miles: 35000

Method of purchase: PCP

Maintenance: Ford Dealership only

Accidents : None

Recalls: None

Under base warranty: Yes

Issue: New onset rattling and amber EML light AFTER a routine service

Context: Issued noted by myself (registered driver) as soon as I drove off the Dealership, immediately after the service, as the car wouldn't go above 35mph and kept "hiccup-ing". I Took the car back to the Dealership immediately (drove less than a half a mile before I realised something was terribly wrong). The technician at the dealership checked out the issue and indicated that it was a "fractured" spark plug (brand new plug). They apparently tried to change the plug but it happened again and so they put in the "old" spark plug (the one the car had before the service). The car went back to how it was before it came in for the service (started running fine again). The next day there was a constant rattling noise (more so during a cold start) and after driving near 60 miles the Amber EML came on again (no performance issue though - kept running as usual). I called the Ford dealership again and they advised taking the car to the nearest Ford Dealership--> I did that but had to wait 10 days for the appointment (drove < 10 mile Distances at low revs in the interim, only IF needed). The nearby Ford dealership checked out the issue briefly and said "we're not dealing with this, this needs to go back to the previous dealership". This dealership found that there were fragments of a spark plug "on the slam panel" and that Cylinder 1 had signs of "bone scoring" and that the cylinder needed "further examination ". Since then, I managed to get a recovery service to drop my car off at the "original" Ford Dealership. They're going to try and "investigate" what the issue is and theyve advised that it might potentially involve me paying for this 

 

Issues preceding the aforementioned problem: none of note. The car ran absolutely fine, seemed very reliable before all of this

 

Key questions:

1- Would it be normal for them to ask me to pay for something that isn't seemingly a part of normal wear and tear or due to customer negligence?

2- Aren't engine faults covered by Ford Warranty?

 

You shouldn't be paying for anything, including having the car recovered and transported to the original dealer.

I can tell this is going to get very messy, very quickly. From experience I would recommend getting a solicitor now and let them deal with the garage.

The cost of a solicitor which can probably be recovered from the garage will be far cheaper than the cost of a new engine which is very likely what you now need.

It is always possible for a spark plug to crack during assembly. Even the slightest misalignment of the socket can place stress on the porcelain, causing it to crack. For this reason, I always use a magnetic socket without a rubber insert to hold the spark plug. A magnetic socket allows for minor misalignment without directly loading the porcelain, which significantly reduces the risk of cracking the spark plug during installation.
 

In this case, it is highly likely that porcelain fragments from a cracked spark plug fell into the cylinder during the removal of the first or second broken spark plug. Porcelain fragments are extremely hard and can easily cause scoring or other damage inside the cylinder.

In my opinion, this is a clear example of poor workmanship. If a cracked or broken spark plug is identified, all broken pieces should be removed before the remaining portion of the spark plug is extracted from the cylinder head.

I strongly recommend involving an independent specialist before the Ford dealership disassembles the engine, as this would reduce the risk of evidence being altered or lost. There is only one opportunity to correctly diagnose the root cause of the damage, and that is during the initial disassembly.