Misfiring, coil pack change, now undriveable

[danford]

Morning all, firstly I'm not great with cars and terminology lol. I have a mk1 focus, it was misfiring so as I changed the spark plugs not long ago I changed the coil pack (an issue that rears it's head now and again, all I do is change sparks or coil pack, or both and its good to go again). So to give you a clear idea, when you come to change gear and accerarate the revs go up with very little accelaration then the revs drop down and speed goes up, it doesn't happen every time but it's been getting worse over the last week This time however, when I changed the coil pack and started it up it just makes an obviously wrong noise, sporadic idling and chuntering, revved the acc pedal a little and it sounds awful. I dropped the new coil pack on laminate floor when opening it so I changed it bk for the old one but still the same problem. I literally undid the bolts and the plug, took the 4 leads off and swapped coil pack then replaced leads etc. The leads only go to one point on the c pack so they're not mixed up. First thing I thought is maybe the leads as they haven't been changed for a cple yrs, plus one of the metal connector bits was hanging out the rubber bit on the lead after I took it off one of the points on the coil pack. So it was totally driveable yesterday, just with a little misfiring and now, after only changing the coil pack, it's obvious it isn't gonna drive properly. Any help much appreciated

[Jimpster]

get the codes read, put the bits back to make it run even roughly and go from there.

[danford]

Thanks for the input. Tbh I wouldn't be able to get it to the garage until at least monday now. I could get some leads for 12 quid today, do you think it's worth a gamble? It had the rev issue perhaps 5 times in a 20 mile journey so the car was pretty much sound, no massive chuntering or juddering, just high revs briefly a few times. The only thing that happened was the coil pack changing which is simple, and the leads disconnected and replaced. If 1 out of the 4  leads was faulty and only 3 worked, do you think it would make an obviously faulty noise/irregular idling rhythm while idling?

[danford]

Also, the codes were read about 4 wks ago when I took it in for him to look at regarding something else and he said then they were showing no problems

[Jimpster]

even 1 lead can cause an issue, process of elimination as to which one if it is, do you have a voltmeter put a current thru each one. £12 is neither here nor there and youll know you have good leads.