Apologise in advance for a million and one posts but this wee forums a godsend for info...(and peace of mind)

Anyway spent the afternoon cleaning the fatty and topping up antifreeze ect..car was sitting idling for about an hour..got in the car and accidently blipped throttle...then noticed everytime I blip throttle I'm getting a small blast of white smoke? Also getting a small misfire from exhaust? Its the first time I've noticed it tbh..car has only recently been put on the road and had been in my garage for 4 months whilst I've been pottering around with it..

If it were me I wouldn't have left an engine idling for an hour, it doesn't do them any good. take it for a blast along the motorway and see how it is after that

Will give it a bash now..honestly never knew that leaving it idling would cause an issue..only left it on to bleed air from system after topping up antifreeze...smokes not excessive but I haven't noticed it before tbh...

With it sitting on idle the water vapour has probably pooled in the exhaust - a blip of the throttle will blow it out as steam .. as 47p2 suggests get it warm with a blast then see what it does

Simon

Just had her out for a good hour around the bipass..all good now...what I did notice before I set off was a sound of water inside the exhaust back box..as you say its been steam! The noise must have been the steam being forced out causing panic within Only thing that worry's me is the car sat in my garage for a few months whilst I was working on it..i had it idling 2/3 times a week during that time..could I have caused damage? Back box is probably rusted inside so lesson learned..cheers guys

Expect on cold mornings, to have steam out the exhaust. It re-enters as you car cools down. And it reboiled out etc.
So, normal....
What I have noticed on older classic cars, is that if you have a small amount of cylinder head valve stem seal wear, whilst idling at say traffic, or like you were, the oil will run down, at tickover, and sit in the inlet manifold, and wait for a 'rinse' of petrol, to take it through the engine, and the driver behind will notice a puff of smoke. This is common on older designed engines, but could be but not likely, a cause of your smoke.
If you see smoke on the overrun, i.e. Slowing down, (in gear) say, this would indicate piston ring wear.
And if it's puffing out loads, it's breaking up, and has scored the bores, and you are doomed.
Just make sure though, that your coolant level is still good. When cold...

Thanks for input...seems to have been a huge build up of water in the backbox..very pronounced sound in fact! Never realised so much would build up in an hour if I'm honest...there was so much that when i blipped the pedal the noise it caused sounded like some sort of backfire...I'm quite relieved now..