So a few weeks ago I drove my nissan a short distance and it seemed to be running fine. I parked it for about 2 hours and then it failed to start after that. The engine turns over but nothing. After asking my brother who is knowledgeable about such things, he suggested it was either no gas or no spark. I replaced all the spark plugs and wires and the fuel filter. Still no start. I tested the fuel system and can verify that gas is flowing and I can also verify that electricity is reaching the spark plugs. I tested each connection coming out of the distributor. So still not starting. With the air filter removed I did notice something new, when the engine fails to start and I stop turning the key, air or vapor or gas is forcefully ejected from the throttle body. My brother says that is a sign that it has jumped timing. Any ideas?