misfire when warming up

[kieronclio]

hello can anyone help me with my valver, if i start it up from cold it will run sweet but after 2mins or so it will misfire and cutout and ive notised abit of white smoke too. first impressions was head gasket could be going but its not overheating at all. any ideas thanks???

 

[ScottyD]

Doesnt sound like its running long enough for you to check if its overheating.
Try a compression test will rule out headgasket or a burnt valve.

Any Engine Management light on?

 

[kieronclio]

i was thinking of buying a tester what would i be looking for just a drop in bar in the cyclinders? thing what happend was the accelarator cable snapped so we towed it for about 30miles with a bar to get it back home but we left it running for about a hour so we had steering and lights etc, when we got back it was misfiring but it didnt over heat in first place