I've got a XH doin the same thing. On hot days go to start in car park has a cough and f@rt then choofs out a bit of black smoke rev it once or twice and clears up, runs beautifully otherwise. I was going to have a bit of a look at carbon canister and vapour lines etc , got a feeling not venting correctly,will let you know if i have any sucess.

Could be the coil pack. Coils are notorious for showing intermitant faults when hot. When you stop you get heat sink and the coil gets too hot and fails to produce good spark. I have a spare one you can have, but I'm in Toowoomba, the postage is probably the same as buying one. Lol

I would wait till it happens, jump out and pull a plug lead, attach old plug and crank and see what the spark it like. Remember to ground the plug and use insulated pliers to hold the lead. If you have dull yellow spark, then this could be your problem.

cheers
Scott

Could be, as I certainly don't blow any black smoke or anything on start up!

As for starting, it doesn't happen EVERY time I start on a hot day ...but enough to be really irritating!

That is generally the problem with coils failing. For quite a while they only play up intermitantly. Definately something to try though. And the best part is it doesn't cost a cent to test. Unless it is actually the coils that are broke...

cheers
Scott