My loved and well used (230k KM, 140k mi) beauty is starting to act up... again. (2000 SE, manual, no mods, CEL on since 2-3-4 years)

The symptoms are:
- random stalling at idle, in neutral, say after 20-30-40 seconds of waiting; (e.g. waiting for at a stop light).
- in neutral inability to hold a steady RPM between 1000 and 3000 RPM.
- bucking at highway speed (100-120KM/H, 60-75 MPH) on cruise control or not (i.e. light throttle), or sometimes at WOT;

When the car stalls I can restart it right away, without cycling the key to off, with no problems at all. If waiting for a stop light I blip the throttle constantly (1000-2000 RPM) the engine may buck/stumble but the momentum keeps everything running. The CEL flashes once (quickly, not like a .5 second on-off-on cycle. It does not flash 2-3-4 times, as it did when 2 coils went a while ago (see below). I can hear a relay being tripped under the dash.

When I try to keep a constant RPM in neutral, as soon as the RPM stops fluctuating due to pedal movement, there is a little buck/stumble, and the RPMs drop 500-750 RPMs. This only seems to be below 3000 RPM. I can hold 3100 all I want, drop to 2900 and it starts to stumble. (doesn't the VIAS kick in at 3000?) The CEL flashes as above.

At constant highway speed (120 KM/H, 75MPH) on cruise or not the buck/stumble is much like the 'bliping' stumble above. If I yo-yo between 100-120, with 20% or more throttle depressed, there is no bucking. (though there is a lot of fellow drivers looking at me like I am a moron, rightly so.) The same also happens around town at lower speeds. The CEL flashes as above.

All this only seems to happen when the car is hot.

'Recent' work on the car:
- 6 spark plugs (platinum) at 160KM, 100mi, 2.5-3 years ago
- 2 coils changed (5 and 6) at 170 KM, 106mi (2-2.5 years ago) All others original.
- Alternator, battery and starter at 190 KM, 120 mi (1-1.5 year ago)

Things I want to try:
- Cruise at 120 KM/H in 4th, which should put the RPMs in the 3500-4000 range (120KM/H = +- 2900-2950)

I have looked around and some mention coils, some battery/alternator, some thermostat, some MAF, some TPS, some vacuum. I think the variable intake might be in there too. All input is welcome and certainly much appreciated.

 

I also have a 2000 Maxima, that has similar problem(s), however mine does not stall yet. Some days are better than others. I changed my Mass Air Flow sensor last year. The problem does not seem to be getting worse but I worry. I have not put it on a diag. machine yet, because my money is funny right now. I hope you post any results that you have. Good Luck.