To think that I'm better than a computer and a team of mechanics!

TBF I've known men be dismissed in exactly the same way. So yes it could have been sexism, but not necessarily (and the managers at both our local garages are women).
But there seems to be a computer says yes/no attitude to everything these days. Obviously you were right in this case!

How likely were you to agree to change the coils when you first raised the issue? Sounds like the fault was intermittent and without a code to diagnose which cylinder was at fault there could have been some labour charges to identify which one was at fault / check spark plugs and cylinders condition etc.

Most customers probably would not agree to this until a code comes up on the ems, regardless of sex.

My late husband could strip an engine and diagnose/fix most things (diesel engine). Garage mechanics were just as dismissive of him as you. He’d order parts and fix things himself and tell them he’d done so when he had to get it MOTd and they were astonished, but still only react to what the EMS said. So no, it’s a sign of the times really more than misogyny.

A misfiring car is unlikely to make it through an emissions test and combined with a lack of misfire data I think it highly likely that most mechanics would come to the same conclusion.

"Given the coil and spark plug change was relatively inexpensive, I’d have rather had it done two months ago. The car will have been running inefficiently all that time."

There was nothing stopping you insisting on a spark plug and coil change if you felt that strongly about it....

Did you notice any change to the long / short term fuel trim?

I had a very similar thing happen to me.... i booked my car in for a service, dropped it off Saturday morning, was met with they haven't got my booking but they can definitely do it on the Sunday. No issues but I had to have it bavk on Sunday due to school runs the following week.
Had a phone call the sunday saying my car wouldn't start, then they got it started but wouldn't sit idle so they couldn't do the service. Listed off some very expensive things it could be to do with the dpf, all saying they could do it that day blah blah. I said to my husband that there was absolutely nothing wrong with my car, starts first time etc (don't think he believed me) rock up to the garage to discuss the work it needed doing. I said I needed it home that day but we'd look at possibly next weekend. I got in the car and the battery was flat. Apparently a garage full of mechanics couldn't work it out and I realised the minute I tried to start it.

Lol, did they turn it off and on again??
Good on you for knowing your car

I don’t understand why you didn’t just book it in for coil and spark plug

My husband is a mechanic (although less general now, he builds engines for high performance cars)
I definitely know ‘more’ now than I used to by sound and feel, can usually tell when break pads/discs needs changing/have warped and also know when a bush has gone 🤣

You could have just asked for those things to be repaired. However, there is distinct sexism in mechanics - my mum rang for a price on tyres once, noted down the tyre size ect and was quoted one price, then my grandfather rang later on to ask the exact same question, same tyre size.. to be told a considerably lesser price.

I’m fairly glad I married who I did, I’ve never had to have a garage experience as he deals with it all 🤣

I dont drive but dh does the mechanics still have learnt to speak to me about car things not all mechanics are sexist

from my experience when booking car in for mot/service they will literally mot and service the car regardless whether I report a issue (unless said issue directly effects the mot or service), if I wanted issue sorted or diagnosed they would then say to book in separately and pay a diagnostics fee?

I have a thing about mechanics always wanting to connect cars to computers I’ll try avoid a rant but I’m yet to come across this method actually solving any issues on a car so if you can find a old school mechanic you have to hold on to them like your life depends on it 😅

however not dismissing the sexism, the chances are had you been a man and said the same sentence of pinking and misfiring it would have probably had a different response yes.
That can be said for any male dominated trade. Recently needed work done and a builder gave me a ‘woman’s’ explanation of the job, I had to stop him mid sentence, he then said he’s just trying to help me understand… he didn’t do the work, I did it myself…

Main dealerships only do the bare minimum in routine/schedule services these days. It's basic a VERY simple checklist, which is mostly observational matters. We've often looked at their checklist after a service and wondered just what they'd done to earn the few hundred they charge.

Latest "discovery" what that our main dealership doesn't even check battery health in services - discovered when the system update wouldn't work, nor would the app to start/stop/lock it, and only then found the battery was running at only 40% so the system shut down when engine not running to preserve it (rather than being "on" to keep it live for the internet).

Before that with another car, it leaked into the footwells for several years. Kept reporting it to the dealership who kept saying they couldn't see anything and kept trying to blame us for not closing the windows properly! Then the heating blower/fan stopped and they farted around having it in several times swapping various components, but it still wouldn't work. Eventually decided they had to remove the dashboard to look at the fan itself which turned out to be heavily rusted/corroded. Then they "discovered" it was a leak from the scuttle board that dripped directly into the air intake for the heater, so basically water flowing through the blower fan and then into the car! I did some internet research and discovered the scuttle board seal was a known problem with that make/model, so really should have been on the service schedule to at least check it, but, no, not on the schedule so garage didn't look!