When you say it is cutting off it will not idle at all or is it stalling sometimes? let me know ROY!
You said you inspected the Idle speed control valve? was it raising the idle up with head lamps on or the A/C let me know, also does the check engine light come on?
I know you said you checked the air flow meter, there is a replacement air flow meter and a reprogram for the maximas , have you inspected this, they will show a lean condition with a scan tool this would be an indecation of a bad air flow meter. I have replaced a lot of these for the maximas low idle and rough idle problems when warm Thank You, XXXXX XXXXX know if you have any more questions, ROY!
The way to inspect the air flow, they dont set a code what happens is the mixture goes to a lean condition, I monitor the alpha readings with a scan tool and the 02 sensors to see if it is lean. If it is,you will need the updated Air Flow and reprogram for the new meter,Thanks ROY!
If you create a vac. leak the engine runs better? let me know. ROY!
The engine is running to rich if loading up with fuel , I would check the fuel pressure regulator make sure the is no fuel in the vacuum line as if the diaphragm could have broken letting fuel go into intake, Also check to see if fuel pressure leaks down when sitting like an injector hanging open not seating letting fuel into the cylinders
Let me know, ROY!
I am not sure what valve you are talking about, if the is water and oil in it I dont think it is working. If you have a misfire warm , you will need to figure out what cylinder is misfiring unplug each coil one at a time when warm to see what cylinder is not changing, this will tell us where to go to figure this out. Thanks ROY!
I have replaced a few ISC idle speed control valves , what also happens when they go bad it can short out the ECM and not allow it to idle correctly