My new 235 000 km 420 SEL always has very rough idle for 5 to 7 minutes, till warm enoug, and then is perfect. Dealer's mechanics and I tried everything I found on that marvelous forum, change or tried new : All filters, sparks, wire, injectors, EHA, coolant temperature sensor,ignition control unit, adjust valves, tried few cleaners (BG 44k, for more than $40 can), leak test, compression test...Timing chain with a 12 degree extension have to be change in a few days but i expect no results on idle... Lot of canadian $$$! Nothing works except unplug coolant temperature sensor for those feuw minutes, what do a fair but imperfect job. Can someone explain what this mean ??? And if one find what is in trouble, I'l give him a very big virtual kiss !!!