i noticed that my cars idle has been prety rough lately . i did some searching on the forums but none seem to be exactly like mine .

i always warm up my car before i take off and the idle is fine ( about 750 ) +-
but when i get to where i am going and actually park i notice the idle is way outta wack .
ill sit there and watch it drop 100-200 rpms for about 3 secs and the car will shake a good bit then go back up .
and every 20 - 30 seconds there is a loud THUMP sound . when it makes the sound you can feel the whole car move with the thump . its like someone gave the car a good nudge .
Take a steel hammer and pound on a concrete floor and thats exactly what it sounds like .... and feels like too ....


when i push the cluth in the rough idle is still there ( drops 1-200 ) but the thump will sometimes completely go away and sometimes ( rarely ) it will still be there but a little weaker and with longer intervals ... about 1 minute

i know they dont have the smoothest idle in the world but its the big thump that worries me .

just wondering if anyone has ever had this problem and what it turned out to be .