I have a 98 Cedric w/ 136000 km. Lately the car has been acting up during start up. It would idle at around 200-300 rpms and causes the car to shake. Also the exhaust comes out excessive and blacker than usual. At times it would even die out, especially when I am coasting to make a turn and I let go of the gas. It would start up fine though and if I give it enough gas it would not die. Acceleration is very sluggish when the idle is real low. Then without doing anything to the car it would just go back to normal operation. I mean the rpm is around 700, the exhaust is normal, there's no shaking and acceleration is normal. I have taken it to the dealer but all they told me is the the O2 sensor should be replaced soon. I had another mechanic take a quick look at the car and he told me that it could be the idle air control valve. I have searched thru the forum here and found nothing specific for my car. Can anybody give me guidance on how I should go about troubleshooting this? Any help will be greatly appreciated.