When going between 10mph and 50mph my car will sometimes make a popping noise (kind of like a fart..haha). Its coming from the hood. Before I had changed my cat converter it was doing it worse. I also changed the spark plugs and stopped completely but then a few days later it came back.

When my car is in neutral and i press the gas it doesn't pop. Only when in drive. It tends to pop more when going up hill. Not nearly as much going down hill.

What could this be? tranmission problem? spark plugs not tight enough?
Please help

 

nm guys thanks for the help but i figure out on my own that it was the spark plug wires the whole time. changed them my self and car runs great again!!!