the car runs. but shakes violently when turned on. on 1993 Nissan 240SX

when i start up my car, the engine seems to shake really violently. it will soon settle down but then starts back up again. and also it makes a putting sound.

The KA24DE engine in your 240 has a four cylinder engine if one cylinder is not contributing to the engines performance the engines performance will suffer by 25%.
Putting sound that sounds like a big exhaust leak that increases with engine RPM could be a spark plug that has blown out of the cylinder head.
I have sen the intake manifold fail but it sounds like your car has something more critical wrong like a failed fuel injector, or spark plug, perhaps something more serious.
1 more answer
i had the same promblem in my 92 240sx ka24de. I first started by geting timing done, then i changed out maf and last but not least, i checked for any shorts. For some odd reason the ealier nissan motors then to lag when a short is present. For more info, contact me @