my lovely lady wifes driver is poorly!!! it's a j reg 1.8 on a pierburg carb and yesterday it started belching out LOTS of steam from the exhaust. checked the coolant and it was kinda low. No signs of oil in the water and no water in the oil. Ive done a sniff test which was fine, compression test was also ok. I've removed the intake manifold and the rubber o ring wasn't totally blocked (the bottom half was a bit gummed up but not bolcked). The base plate of the carb is pretty shot tho, also the plugs were very black and sooty. She has said that the car has been reving up a bit of its own accord when cold. Is it possible that its running really rich and this is causing all the steam?

I'm a bit stuck as i was hoping the o ring would be totally blocked and replacing it would sort it out.
Anyone got any ideas??? Need to get the car back up and running asap.