I Pulled my Codes today and got these:

P0300-Randome Misfire
P0113-Intake Airtemp-CKT system something..
P0171-Fuel System-To Lean Bank 1.

Alot of this Pointed toward a MAF. SO i bought a new one, put it on, car now revs nicley ...

But my idle is kinda weird.. it dropps down to 400-500.. then back up to normal 750-800 at idle.

I cleared the Codes drove about 5-6 miles no Check engine light YET... but why the irratic idle ?

 

Probably have to do an idle relearn or reset the ECU.

 

as far as the idle... on start up my car does the same.. probably have to do what he said ^

 

how do you do a idle re learn?

 

I belive its automatic, you just have to drive for a while.

these codes could also be related to a bad injector(s) if you are getting a missfire and a lean condition.

try to put some fuel injector cleaning in the tank.

 

here is how to do the reset, mine does the same and i did the reset but didnt made any differ, but ive done my headers and its running rich and im guessing its cus of that.

Accelerator Pedal Release Position Learning

Operation Procedure
1. Make sure that the accelerator pedal is fully released.
2. Turn ignition switch “ON” and wait at least 2 seconds.
3. Turn ignition switch “OFF” wait at least 10 seconds.
4. Turn ignition switch “ON” and wait at least 2 seconds.
5. Turn ignition switch “OFF” wait at least 10 seconds.


Throttle Valve Closed Position Learning

Operation Procedures
1. Make sure that accelerator pedal is fully released.
2. Turn ignition switch is “ON”.
3. Turn ignition switch is “OFF” wait at least 10 seconds.
Make sure that the throttle valve moves during above 10 seconds by confirming the operating sound.


Idle Air Volume Learning (Throttle Position Learning)
It is better to count the time accurately with a clock.

Operation Procedures
1. Perform “Accelerator Pedal Released Position Learning”.
2. Perform “Throttle Valve Closed Position Learning”.
3. Start engine and warm it up to normal operating temperature.
4. Turn ignition switch “OFF” and wait at least 10 seconds.
5. Conform that accelerator pedal is fully released, turn ignition switch “ON” and wait 3 seconds.
6. Repeat the following (steps 7a, 7b) procedures quickly five times within 5 seconds.
7a. Fully depress the accelerator pedal (HARD)
7b. Fully release the accelerator pedal.
8. Wait 7 seconds, fully depress the accelerator pedal and keep it for approx. 20 seconds until the Check Engine Light (CEL) stops blinking and turned ON.
9. Fully release the accelerator pedal within 3 seconds after the CEL is ON.
10. Start engine and let it idle.
11. Wait 20 seconds.
12. Rev up the engine two or three times and make sure the idle speed and ignition timing are within the specifications.

 

I had a similar problem, I got a lean code (I forgot the exact code) and I had the MAF replaced as well as the ECM reflashed and updated. Does he act worse in cold? Because when the Nissan tech was reflashing the ECM he told me there was an update for cold start as well as another one I forget. After getting those two things done my car revs nicely and idles nice. The ECM reflash/update is like... 100bucks? MAF sensor I have no idea because I used to work at my local Nissan dealership and I get the hook up =D My total after MAF and installation, ECM reflash/update $182.00.

 

My Max pretty much has the same symptoms with the erratic idle on cold startups. The car fires up, revs at about 1500, then drops the idle and sounds like it's misfiring, then recovers to 1500 and repeats for a couple minutes until the car get's to a warmer temp.
Any idea what that "update for cold start" is?
I did replace my IACV about 10 months ago and never did the idle relearn as it had always idled fine...up until the winter.