Hi everyone, i have an 06 altima 4 cyl . it's idling rough. Seems to get worse if i put it in drive. If i put it back in park, it goes back smooth for a few seconds then gets back rough. No check engine codes. New plugs and wires. Gas mileage is awful. When hard acceleration does not hesitate. Does smell like gas under the hood strongly when idling .. Any ideas?

And do these cars have only one fuel filter and do they have a fuel pressure valve?

Did you get this resolved? I would disconnect one spark plug wire (remove the coil) at a time to see if it doesn't make a difference on one of them. You may have a bad coil-on-plug?

check the connection at the coil on plug as well. Oil in the spark plug tubes? If yes replace the valve cover (dealer part to avoid getting a faulty valve cover). Here’s my theory on the gas smell. Maybe you have a leak at the intake manifold where it intake mounts to the head. Jack the car up and look at the bottom of the intake manifold where it mounts to the cylinder head for any signs of a leak. Spray throttle body cleaner at the intake manifold, also spray the vacuum lines that goto the intake. A change in the engines idle will let you know where the problem is. Do this while the engine is cold. Caution the stuff is flammable so don’t get carried away.