I have a 2002 Nissan XTerra. I'm seeing VERY bizzare, complex behavior.
Most of the time I'm driving it it drives and idles fine. But periodically (Say, every 5 to 10 minutes), while idling it just shuts off. If I feel the stall is about to happen I can rev to keep it alive, but while revving it runs VERY rough, chugs (no pops), and spits black smoke out of the exhaust. USUALLY once I get the revving up to 2500-3000 rpm it "catches" and starts smoothing out and running smooth. I've never had it start running rough while the car is moving, but it has stalled when I was cruising with my foot off the gas, and I had to tap it into neutral and re-start the motor. Very rarely, it seems to continue to run rough (feels almost like a miss) even though the rev cycle. Usually after 5 to 10 seconds of this it wakes back up and is fine.
Most of the time when it cuts off, I can start it right back and it runs fine, but sometimes I start it back up, and it does the rough-running, and won't hold an idle.
When it is running fine the at-temp idle is about 600RPM. Sometimes it'll shutter and fall down to around 400 and then recover. Sometimes it doesn't recover and unless I goose the accelerator, it will die.
There is no SES/CEL light on. that only comes on when the motor dies and the car is still in the "ON" position. But as soon as it starts back the light goes back off (as expected.) I still hooked a scan-tool up to the car, and it reported no diagnostic issues.
I hunted for a vacuum leak using the old fashioned "spray brake
cleaner" method...noticed nothing. I don't think vacuum is indicated, since the car runs fine most of the time.
My initial gut was to just crank the idle up a couple hundred RPM (as this seems to only start happening once I let the car return to idle.) but the fact that MOST of the time it holds the 600RPM idle just fine, and the fact that it sometimes exhibits the problem outside the idle range made me finally think adjusting the idle up wouldn't fix anything, so I opted not to do that.
I have visually inspected the MAF sensor and the leads on it look light-grey and clean. No black, no fur. I also visually inspected the cap and rotor button, and all the pickups and the rotor itself looked very clean.
I've had the car over 2 years. I *BELIEVE* that the previous owner said he had a tuneup done recently, but cannot swear it. The plug wires look fairly new, but who knows, right?
This behaivor started yesterday morning. Before this the car ran like a top.