This is really general, i know, but i've been trying to track this problem down for a couple of weeks now..
97 taurus GL, vulcan 3.0 engine. it's got about 160km (100,000 miles) on it. It has an intermittent rough idle, it's more noticeable especially when the engine is cold, or if the A/C is on. I replaced the plugs and wires, that didn't change the condition at all. I've also noticed it sometimes takes a few seconds longer to "catch" when cranking the engine. This leads me to think it could be a coil issue? The car is quite well maintained as far as scheduled service goes. I don't know if this is related, but the trans seems to be shifting harder then it used to, the idle and the shifting seems to have cropped up at the same time.
No codes, no check engine light, nothing. I'm just a little worried that when the weather turns cold here (Ontario Canada) that it'll be more then just a rough idle, and i hate doing repairs in -40 weather...