Dear Sir, I just bought a car.

"I open the engine oil cap the was coming outside some one"

Please restate that properly and with some punctuation so we know what you're asking.

It's common for oil to spray from the cap when you remove it because it is being thrown around by rotating parts. If a lot of air is also blowing out, that could be due to worn piston rings.

The place to start is with a compression test. If the numbers are low or uneven, follow that with a cylinder leakage test. That will show why the compression is low. There can be leaking intake valves, leaking exhaust valves, worn piston rings, or a leaking cylinder head gasket.