It has a 16hp Briggs and Stratton engine. A couple weekends ago I went to mow, tried starting and hardly spun it one rotation. Started going through everything it could be and ended up deciding it was the starter solenoid. Took it to my local dealer, they tested it and said it was bad. Got one that isn't quite the same as the other and installed it. Ran fine and mowed my whole yard. Tuesday evening I went to mow again. Started right up, drove out of the garage and revved it up. 3 seconds later it started smoking sputtering and died. Had to choke it to get it started again and ran like complete crap. Idle was rough and anything over 1/2 throttle it would start smoking and die. Took the engine cover off and opened the carb to the air and took the spark plug out thinking it had flooded itself, there was gas all over the plug. Week later I installed a new spark plug since the mower was backfiring when I would shut it off. Started up and seemed to run fine. Pulled out of the garage, let it run at half idle for a while, then wide open. Ran fine wide open for about 3 minutes then same thing. Smoking like it was burning oil and died. Any idea what is going on?