Nissan Repair: 94 nissan altima, air control valve, nissan altima

Question
it starts and drives ok but when it warms up and i stop the revs will drop down to about 400-500 rpm then back up to about 800-900 rpm. drive fine but after about 10 mins drive it. and when i stop it will drop down then stall it rstarts fine .i have noticed a small amount of oil from dis body, this was replaced last year by previos owner.

Answer
Mark,

Sounds like the idle air control valve is sticking.  I would clean the throttle body and the idle air control valve to make sure it is clean.  If you notice a large amount of oil on the surfaces in the throttle body I would be looking at an oil additive to keep blow by to a minimum and change the Positive crankcase vent valve.  Also, if the plugs have not been changed this would be a good time.