I have a 99 Impreza thats completely stock and I've been having some idle issues lately. Had a look under the bonnet earlier with no real idea as to where to look first. The car when cold starts up at about 2500 rpm and warm about 1500 and when idle it goes up and down constantly. I found out that the throttle cable was wound up a bit too much so i lossened it and it went back down to its normal idle for a little while. Then it started again, but this time it idled at 1500 and went up and down. I noticed the throttle anchor wasnt completely touching the metal rod that stops it I dont know if thats the issue? If so then how can i fix that and if it isnt that what could be causing this rough idle? I have been advised to clean the throttlebody but i havent gotten around to that yet,

Hi - you mention the car is stock but cables have needed adjustment....

I would look at the MAF, when was the air filter and plugs replaced. Are all your earth points good, is there a good voltage from teh alternator to the battery?

Some straight forward stuff you could look at as well