Funny noise on first start in morning

Hi all! When I started my car yesterday, and agin today, for the first time in the morning, I got a thwack-thwack-thwack sound from the engine...first time I've ever heard it. It goes away in a few minutes, and was accompanied (at least yesterday - it was dark this morning) by a light gray (oil?) cloud from the exhaust. I recently had the 180k (90k) mile work done and they adjusted the valves. I have 197k miles on the car, and checked the oil level this morning, and it looks ok...what else should I check? thanks!!

black/Grey smoke is rich fuel, white smoke is oil. If it is just a puff at startup, it could be valve guides if it is white smoke. Valve adjust at 90K? Sounds way too early for a valve adjustment. this is a solid lifter motor so there is not supposed to be a valve noise. How loud is it? might be a sticking injector as they are the loudest thing on that motor at idle which is a testament to the quality of that motor, hope it is not the P/S pump..check fluid in that.