I have a 2005 Nissan Altima 2.5s. I have just replaced the computer with a used one and it was running better than it ever did before. The other day I went to the store and when I came out the car would crank all day but not start. like it was getting no fire. I've changed the camshaft sensor, checked the fuel pump and made sure it was working, it still won't start. It is getting spark but it is a very weak spark. I'll pull a spark plug wire, put a spark plug in it, ground the plug with a jumper cable and crank the car. I have to cup my hand around the spark plug and get it in the shade to see the spark. It is there but very weak. Any suggestions?