My 85 Nissan p/u stalls when coming to a stop when cold and has varying rpm idle once warm. Sometimes real high and then dropping off to normal.

If it was doing it when cold I'd say definitely, but your problem is when warm right? Maybe throttle position sensor? The ICV is pretty expensive ($85 and up). Just to take it our of the equation maybe clean it. I've never done mine, but Googling it, it doesn't look overly hard. Hopefully you have a garage or better weather than I'm having today!!. Good luck. Hey, when you figure it out come back and let us know what it was.

You don't say what make of car but it's about the same for all. Your problem is the choke adjustment. The choke raises the idle when the car is cold and after warm up drops to normal. You are doing the chokes job when you hold the pedal down, once its warmed up the choke no longer functions till cold again. So check the choke and the high idle speed adjustment. Simple fix. Hope this helps mike

Scan for codes. China OBD2 car diagnostic tools wholesale on CareUCar

will be a sensor problem need to get the OBD read by a suitable mechanic

check the MAP sensor (manifold absolute pressure). The ECM (car computer) uses that to keep idle at minimum 750 RPM. It's normal for it to run high when cold. These small 4 banger motors typically run hot, and they won't run right IF they're NOT running hot, ergo the idle is usually high when it is cold so as to cause it to warm up quicker. If the RPM's drop below 750, suspect the MAP sensor, &/or ECM.

TRY REPLACING YOUR PCV VALVE

Plug the vacuum line you unplugged and the idle should come back. Change your air filter and the map sensor. check for correct coolant level and replace the coolant temp. sensor. This sensor affects cold starting and idle through the ECU (open loop mode, rich fuel mapping and 1200 rpm idle) It should go to closed loop mode in the ECU once engine warm up is achieved ( lean fuel mapping and normal 900 rpm idle). Do not unplug anything else till you perform an OBDII scan of the stored fault history

Check for vacuum hose leaks or component clogs. You can use vacuum pressure tester.
or turn the idle screw down.

Hi, Check all vacume hoses and fittings make sure there are no vacume leaks also make sure ignition timing is correct.