Hi, I have a 90 911 c4. It starts and runs with no problem. When I stop the engine and try to start it. It won't start but if i wait about ten minutes it start right up. What could be causing this?

Another problem I have is oil leaking on the muffler and makes it smoke alot.
Is there a special oil or product that I can use to help with this?

 

Sounds like a bad DME relay to me.

The special product to fix the oil leak is called new gaskets, more than likely your valve cover gaskets. But if you want to do a full rebuild, then dump in some miracle cure