I have a 99 Nissan Maxima GLE. It has about 80,000 miles on it. The problem is that while idle it feels as if the engine is dropping. It also sometimes does it while I'm driving (30 mph). As if its hesitating to go faster.
But basically the problem is when I'm just idle, still in drive, but waiting at a light. It just drops and sometimes it does is 5 times in a row.
The mechanic said it was the knock sensor, so I had that replaced. It was good for about a week, but now it does it again. I've read some things that a knock sensor is if you hear knocking sounds. My car does not make any knocking noises. It is silent, but the car just drops.
Not too sure why a mechanic would up and blame a knock sensor right off. It usually only trips as a result of something else. Sounds like he may have been farming you for some additional repairs in the future. The knock sensor may be throwing code as a result of a heavy sputter in your idling condition. I would venture to guess that you are probably going to show some other codes if you have it diagnosed with a reader. Most likely you will see a lean condition code, or possibly some random misfire codes. Tough thing is to say specificly what is causing this. Your best starting place is to have all of the intake vacuum points checked. Once you determine it to be something else(unless that is the culprit) move through the rest of the combustion cycle.
This is one of those issues you can find yourself swimming in information for, but may also lead you to a last possible problem solution. I'm working on a similar problem right now with my 01 Altima, and only have a couple possible culprits left. PM mem if you interested in the specifics on that one.