06 Rainier intermittently puffs grey cloud of smoke

[Alan Anderson]

I recently bought this 06 Rainier and like it a lot. But I have noticed a number of times that I'll be driving along at freeway speeds and suddenly a large puff of grey smoke belches out very briefly and then all is well. I notice no change in engine speed of feel any hesitation at all. I just notice a big puff of smoke that makes the drivers behind me nervous. It happens both in cruise control and not. I do not detect any fluid losses so far. I have no engine codes or messages. All my gauges seem to be in the normal range. As I have had family medical problems and several cars go bad in the last year I am not too financially well off.

Can anyone suggest what I should do? I had the car thoroughly checked out when I bought it and they found no big issues. As this is very intermittent, maybe once or twice a week, I don't know what the garage might be able to do to check on this. I drive about 50 miles a day, maybe a bit more.