Juice coming up through the chimney is usually a sign your tank is slightly flooded or leaking. Try giving it a flick with the drip tip pointing downwards, that usually clears out any extra juice in the chimney. Try vaping it again, and hopefully it will be ok. If it happens again, it seems that your tank is leaking through the coil. Let us know what tank and coil you are using...
might need a bit more power through the coil as it may be boiling rather than vapourizing the juice....... have a bit play around with it taking a vape or two while holding it upside down can sometimes clear the coil n'all