i've been having a misfiring problem with my 96 240. Basically what happens is the car "bucks" and the RPM drops. It usually occurs in first or second, while either shifting gears or just crusing. It first happened really badly three months ago, so i changed the spark plugs and it got much better. Two weeks ago it happened again, and a few times since. When it happens, it will usually be more than just once. I work at a Nissan dealership so i asked some mechanics to look at it. None could come up with a certain diagnosis, but they did have some suggestions: 1. Mass air flow, 2. O2 sensor, 3. Timing chain, 4. rotor cap.... I haven't even been able to find any consistent patterns as to when the knock happens (engine hot/cold, etc). So since mechanics can't help me, i'm basically looking for somebody who has experienced a similar problem and who might have some suggestions. Thanks