Since I got back from Orlando on Saturday (I live in Jacksonville Fl) my idle rpm will increase to 1500 with the clutch out in neutral and then with the clutch in will go back down to about 1000. This happens for a couple miles on the way to work and does not happen at all on the way home.

So, I guess it is related to the engine warming up. In the past the idle would stumble pretty good at the point I assumed the car decided it warmed up to operating temp. Never figured out what is was (thought maybe afr changing over).

I currently have the M flash, stock plugs, and 19,000 miles.

I have not gotten my recall letter yet and am apprehensive to take it in till I do more reading in here.

Any ideas? MAF, plugs,...?

 

About nine miles home at a stop light in neutral with clutch out the rpm started going from 1500 to 700 about every second and a half. I let it go for about 5 or 6 cycles then put the clutch in gave it a little gas, let it out and back to normal.

 

maf or o2 sensor issue i would think BUT your second post makes me think the tiny neutral switch on thtranny is sticking. this switch tell the computer when you are in nutral. if it sticks the pcm gets conflicting signals and has difficulty idling

 

Yah, good thought. Thanks

 

My miata would do this from time to time, idle at 1k and jump to 1500, about 2 secs at each lvl. Turned out to be a bad connection to the idle valve on the throtle body. The sensor was good, so we pulled it, cleaned the contacks and put some wd40 on it and reconnected it, worked fine.
maby its the same thing