I have a 1992 VW GTI 16 valve with an idle problem. At idle the engine hunts for an idle speed between 1000 and 1500 rpm. It cycles quickly between the two rpm levels, about every second or two. When the car is at speed it runs fine. Pior to doing this all the time, it would do it occasionally while driving in traffic. When it did, I would shut the engine down while coasting and restart the engine after 10 to 20 seconds, after which time the car would idle fine, occasionally I would have to do it more than once. Now it does it all the time, it doesn’t seem to be related to any conditions such as: engine temperature, ambient temperature, weather conditions, time of day. I thought the obvious solution was to replace the idle control valve, at great expense, however, it did not affect the idle control at all. I now appear to be out of answers, any direction would be appreciated to help diagonse this problem.
A vacuum leak can cause the idle speed to vary.
mcparadise, thanks for the suggestion. That crossed my mind and I checked for any vacuum leaks and could not detect any. Sorry, I should have included that in my original post.