Hi everyone, I am new to this form and hopping that someone out there might have some knowledge on my problem. I have a 2000 Ap1 that I have owned for 10 years or so that has done 83,000k and have developed a rather harsh vibration at high idle i.e. cold start idle and not moving, this is not present when it is at running temp 1000 rpm and is less noticeable above 4000 rpm. It feels like a misfire but after many checks this don't appear to be the problem. Things that have been check and done include a trip to Honda to see if the computer/ mechanic could find anything (yes I know was a waste of money) and they checked all of the electrics injectors coils etc and nothing abnormal. It has also been to another shop that I know and trust and they have spent many hours going over the car and they have given up now too not being able to find the source of the vibration. They have been very through and have not been able to fault the engine in any way and have removed replace exhausts aux belt engine mounts, done compression test and have recheck all of the electrics on a scope but nothing. If you stand in front of the car running there is no sign of the problem it is not until you sit in the car that you can feel it and again it feels like it is running on 3 cylinders. I have spent about 25k on this car in the last 24 months a lot of that was cosmetic (The car is stock mechanically) but it has had every every thing replaced including water pump, front belt, bearings, harmonic balancer, clutch, engine mounts, gearbox mounts, knock sensor, plugs and coils and just about everything external to the engine. The problem developed during a spirited drive and the only thing left in my mind could be the gear box but as I said this happens sanding still and doesn't change with the clutch in or out. The car still drives fine and it is not really noticeable higher in the rev range and still has no problem going to full rpm under load. Any thoughts would be greatly appreciated