Nissan Altima GXE

The knock sensor will not usually affect idle and such. It detects things like preignition and so on to help computer decide how much fuel to add or remove depending on driving conditions and can also be used to detect misfires (multiple) usually not spark oriented. If you clear the code, does the problem still exist? what year is the car, and what type of throttle body does it have. your problem sounds like a IAC motor that sticks or is out of range. The idle air control motor steps back and forth depending on throttle plate position to allow the car to keep running when the throttle is not open, preventing a stall. this would give you both of the problems u have, and would not necessarily set a code. hope this helps.

Thank you Russell for your response.The car is a 2001 and has 1 throttle plate,not sure what type throttle body is. Problem still exists after clearing code. Marlin