Odd starting problem.

[Toaster Pilot]

My 2010 Kia Rio 1.4 has a bit of a weird problem - sometimes if I've left it standing for a couple of days (or weeks, once) it really struggles to start - first turn of the key it turns over fine, sounds like it's starting up but then dies with a judder, almost like a misfire. Second and subsequent turns it turns over really slowly like the battery is dead and then finally it starts up with the smell of incomplete combustion and runs, drives fine for days/weeks/months afterwards.

Any ideas what's causing it? It doesn't even do it consistently, I can leave it for weeks without problem yet sometimes after a couple of days it does this.

I guess "take it to the dealer" is the answer but I just know they'll not be able to find an intermittent fault because they always struggle with them!

[MjetSport]

Sounds like something could be slowly draining the battery, or just a faulty battery itself. Try a new one on before taking it to any garage.

[Toaster Pilot]

MjetSport said:

Sounds like something could be slowly draining the battery, or just a faulty battery itself. Try a new one on before taking it to any garage.

When it does start it turns over at a normal rate and fires - like it would with a healthy battery - with no charging/jump starting/etc required.