my accord has a very high rough idle. it goes from 1,500 rpm to 1,000 up and down. sometimes it just stays on 1,000 when it is not doing it. it is really annoying. i had it checked and the vaccum hose from the throttle body to intake was dirty but after it was cleaned, it worked fine. then after 2 months, it started to do it again. i checked the same hose but it is clean. so what else can be causing this problem?