Engine misfire then it cleared

Technical Area Engine, Transmission, Exhaust etc
2
Hi all, 
There are a lot of knowledgeable more experienced people on here than me so I am hoping someone might be able to shed some light on a engine misfire I had on a run out yesterday. Filled the car up with fuel to just over half tank and went for a run of around 50 miles through the countryside with other friends in there 5s and we pulled into a country park, paid the attendant and accelerated 1st 2nd then pulled hard left into a parking bay and when the engine came to idle I thought there was a slight misfire got out of the car hand over tailpipe and sure enough the puff of a misfire indeed, opened the bonnet and in turn disconnected the plug to each ignition coil to try to determine which cylinder was misfiring which was inconclusive, engine still running, seemed to rev ok but at idle still misfired, switched engine off for a matter off seconds and restarted and hey presto running perfect again, rest of run was completed ok another 60 miles no loss in performance and at each town we passed through at traffic lights idle was ok. Pulled out spark plugs and checked connectors to coils all seem ok. Drove it again yesterday from a cold start all ok. CEL light goes out on start up no issues there.
Dont think I have a serious problem but would like to know what caused this random misfire that came and went without explanation, anyone else ever experienced something similar?
MK3, 2006, 1.8, 24500 miles, plugs changed @ 18000, oil & water all ok.

Thanks for reading
3

Hmm, just a thought, but the clue might be in the phrase “Filled the car up with fuel”

The fuel might have been contaminated or just too cheap, or something. Or else an injector might be partially blocked such that a small charge doesn’t get through but a bigger one is enough to fire.

Next fill up (after the tank is nearly empty) use a fuel that helps to cleans out the system (such as V-Power) and see if that cures it. It might take a few miles.

Good luck.

4

Hi was thinking fuel myself now had filled it up with Texaco 95 octane I would normally use 97. If it had have been a broken or chaffed wire to  an ignition coil fault would have been found ok it was just unusual the way the misfire appeared then went away again once engine was restarted if it had have been a bad electrical connection you would think the fault would still be there the rest of the day Maybe by switching the engine off then restarting re pressurised the fuel rail and cleared a bit of dirt I don’t know, as i said performed well before and after ok, strange one indeed.

5

Could be a faulty coil pack that is intermittent but that would be at load you would notice it.

Changing plugs at 18,000 miles is a waste of money as they do around 62.5k before they need a change, was that to sort some problem.

It could also be another sensor that is maybe got a bad connection. I wonder maybe a temperature sensor.

My thoughts are if it was iffy fuel you would notice that under load not on idle but you never know.

It can take a while for a sensor to tell the ecu it is faulty still it is not working up to spec.

Maybe worth using a code reader even the MIL is not on but again may be waste of time.

6

Hi again, I purchased the car used and it had been sitting for a year unused so spark plugs where changed at 18000 because they where originals and 8 years old, where tight coming out so was glad to change them. I have a code reader on order.