My car seems to be having some sort of engine trouble, nothing serious, but i feel that it may just be the beginning.

-A few times when i have been standing behind the car and watched someone else crank it up, i see a very brief cloud of dark smoke come out of the exhaust, almost like the engine "coughs" it out when started up for the first time in a few hours.

-It stumbles on acceleration sometimes, not a severe stumble, but if i have to drop the hammer from a dead stop, the car will hesitate for a quarter or maybe half second before it even moves. now, a slight hesitation is understandable, but this isn't a turbo and i can actually feel/hear the stumble. This has become a saftey issue because it can be rather hard to turn out of my neighborhood at times, therefore any stumble or hesitation at all is dangerous.

-This may be an unrelated problem, but the engine seems to drop off suddenly if i let off the gas while cruising at around 40 mph. It almost seems like an overdrive issue at times as i move along and the trans shifts in and out of a certain gear, but it is noticeable. Wasn't sure if this was a trans or engine problem though.

-Lastly, there seems to be a very slight idle problem. The tach doesn't dance around from 1000 to 4000 or anything, but it seems to fluctuate slightly at times, and twice in the past 3 months or so i have felt a sudden drop in idle (just for a half second maybe, then it comes back) at a stop light, it almost wanted to stall on both occasions, but recovered on its own without me having to open the throttle some.

This is all starting to bother me, not to mention acceleration and power, both of which seem to be VERY weak, even for a volvo. obviously it has lost some ponies and torque over the years, but still...

***A similar question, were volvo's power ratings for torque and HP taken at the flywheel or rear wheels? thanks for the info and help.