Hi, My MK1 focus takes about 5 seconds to start, I've Put new Ignition leads in, New spark plugs & Coil pack I don't know what it could be.

I Changed the battery about 3 months ago. Sometimes when I have my lights on they go dim for a second when I'm driving.

Thanks for any help.

its highly likely that this will be the cause of your issue. If the car cannot breathe then it cannot start, or will struggle. The car will try tuirning over, until it builds enough exhaust pressure to the point that it has enough energy to burst through the CAT and breathe, thats when it starts.

As above if the cats clogged youll have issues if it isnt already itll start running badly the dimming lights could be the wrong type of battery depends what you have fitted?

bump

Chris, Arthur and I both replied to you have you explored these avenues!

Chris, Arthur and I both replied to you have you explored these avenues!

I've had a brand new CAT fitted and a coil pack but still the same issue.

That's helpful to know always best to share that information lol.

So new cat new plugs, did you change the ht leads also? Did you check your battery is indeed silver calcium, it should be on the battery itself

That's helpful to know always best to share that information lol.

So new cat new plugs, did you change the ht leads also? Did you check your battery is indeed silver calcium, it should be on the battery itself

I changed the ht leads and my battery is

Does the car have any performance or running issues?

Does the car have any performance or running issues?

If runs fine when it's warm, It idles at 1500 when I first start it, Then goes down as it warms up.

Batteries should be silver calcium not lithium calcium so this won't be helping. I think you will have an idle control valve which will likely need cleaning so I would start by removing and cleaning it. I don't believe you have the mass air flow sensor but if you do It would need cleaning with electrical contact cleaner.