Auto Racing: idle troubles, mazda rx 7, sarasota florida

Question
i have a 91 nissan nx2000...not for racing, just a car to get me back and forth from work...you were the only person i could find that knew well about nissans....my car is having an idling problem.  When i turn it on sometimes it will be perfectly fine...but other times it will rev up and down between 500 and 2000 rpm's and stahl out or even up...ive checked my vaccum system and there are no leaks...i got a new pcv valve, any other ideas of what it might be? any help would be appriciated...thanks for your time
alex

Answer
Hi Alex:

Well, the Nissans I work on are mostly about 20 years older than yours. I have trouble enough with them !

I have a Mazda RX-7 I drive around town which is doing the same thing.  It's probably a malfunctioning sensor of some type, or perhaps a leaky cold start valve, which would occasionally drip fuel into the manifold.

My Dad was a doctor, and even he occasionally had to tell a patient:  "Let me know if this cure works- - -I've got the same symtoms myself !!"

I wish I could offer more help.

Good luck,

Dan Liddy
Sarasota, Florida