My wife's car is a 2004 Altima 4cyl, auto with 80k miles. It has started to randomly shudder which goes away after some seconds or a few blocks. One time it threw off a code indicating a misfire on cyl. #1. I pulled the spark plug, it looked fine (only 10k miles on the plugs). I put the plug back and tested the strength of the coil's spark with a test light/probe and it was strong. Nevertheless I switched the #1 coil with cyl. #3's coil, to see if a misfire shows up on cyl. 1 or 3 (I didn't move the plug), and have been waiting for another check engine light/code; none so far, but the shudder randomly continues. I think a code will come after x number of shudder incidents. So, while I'm waiting for a code I thought I'd ask for thoughts & ideas. Anyone have any?