How many RPMs should the engine idle at?
Registered User
Joined: Sep 2006
Posts: 637
Likes: 0
From: denver
depends, when it's cold out and the car just started and I have the heat set to auto, it idles at about 1200 until it gets warm, then goes down to about 700... when the AC is on full blast in the summer it's around 1000, but no ac, no heat, it's about 700 most of the time.
Trending Topics
1100-1200 RAWR...I need to get that fixed...Nissan Hawaii wont adjust it for me tho...lol
1st Nissan Florida bumped it to like 900 when I had my tilton installed then Techno Square accidentally added a bump too cause they thought it would over ride my Nissan bump and I ended up with the high idle...I then thought Turbonetics reflash would knock it down a little but it didnt and Hawaii nissan wont do it for me...yikes
1st Nissan Florida bumped it to like 900 when I had my tilton installed then Techno Square accidentally added a bump too cause they thought it would over ride my Nissan bump and I ended up with the high idle...I then thought Turbonetics reflash would knock it down a little but it didnt and Hawaii nissan wont do it for me...yikes
Registered User
Joined: Oct 2003
Posts: 984
Likes: 0
From: Marietta, Georgia
Once you set the idle at correct rpm and the dynamic IAC percentage correctly and changes after warm up should be an excellant indicator of problems beginning.
I use the IAC % duty cycle [OBD2] to tell me when to clean TB [idle drops],
You cannot rely on dash tach to tell you much at low rpms it is pretty inaccurate and hard to resolve 25-50 rpms.
Higher than necessary [for smoothness] idle just wastes gasoline.
I use the IAC % duty cycle [OBD2] to tell me when to clean TB [idle drops],
You cannot rely on dash tach to tell you much at low rpms it is pretty inaccurate and hard to resolve 25-50 rpms.
Higher than necessary [for smoothness] idle just wastes gasoline.
Registered User
Joined: Oct 2003
Posts: 984
Likes: 0
From: Marietta, Georgia
IAC = idle air control
On older engines this was a separate bypass around the TB [a screw adjustment to manually set % of air and more importantly a solenoid bypass [that pulsed in addition air/time] around the manual part so ecu could add enough extra air to get 1500 rpm [to act as a throttle dash pot on deceleraation and to increment air under AC, power steering, and alternator loads- lights,etc]. 10-15% duty cycle of just no load idling , add AC =35%, turn on lights more, turn steering more...........AT 60 mph duty cycle 70% so when you suddenly let off throttle the rpms don't fall to 650 and the engine doesn't die.............progressive drops in duty cycle as the car slows down.
Modern cars intergrate this in TB plate motor software so ecu cracks throttle to accomplish same thing.
Why you calibrate throttle pedal closed potentiometers [voltage] and then ecu adds addition voltage to TB motor.
Modern TB [with motor to control] are very very sensitive of solvents [spraying them in TB can cause expensive TB failure]............time consuming [labor expense] Q tips and cloths very very little solvents. Older cable controlled were almost indestructable.
On older engines this was a separate bypass around the TB [a screw adjustment to manually set % of air and more importantly a solenoid bypass [that pulsed in addition air/time] around the manual part so ecu could add enough extra air to get 1500 rpm [to act as a throttle dash pot on deceleraation and to increment air under AC, power steering, and alternator loads- lights,etc]. 10-15% duty cycle of just no load idling , add AC =35%, turn on lights more, turn steering more...........AT 60 mph duty cycle 70% so when you suddenly let off throttle the rpms don't fall to 650 and the engine doesn't die.............progressive drops in duty cycle as the car slows down.
Modern cars intergrate this in TB plate motor software so ecu cracks throttle to accomplish same thing.
Why you calibrate throttle pedal closed potentiometers [voltage] and then ecu adds addition voltage to TB motor.
Modern TB [with motor to control] are very very sensitive of solvents [spraying them in TB can cause expensive TB failure]............time consuming [labor expense] Q tips and cloths very very little solvents. Older cable controlled were almost indestructable.
