Erratic tickover on 93 Sportrak ELXI


Hi,I've got a problem with a high tickover at idle. This seems to vary from about 600rpm to 1400rpm and does not have any particular pattern. Screwing-in the slow-idle screw on the manifold has helped a bit but I'd really like to cure the problem. The guy at the local garage says it sounds expensive! Any advice/help would be greatly appreciated-especially as I don't have a fortune to spend!