I have a 2006 G35 6MT Coupe with 86k+ miles on it. I was traveling all winter, so the car sat for 5 months from November until April. There were no issues at all before I parked it, and the whole time it was parked the battery was attached to a trickle charger. When I started it up about three weeks ago, the car fired right up with no issues which tells me the battery stayed charged the whole time as it should have been.

I did not notice the high idle issue right away since I figured it was just cold. However driving around I've noticed the car is louder than it should be when I am stopped at the lights, and it was doing other unusual things. This is when I noticed that even at normal operating temperature the RPM seem to sit at 1.4k. I first thought it might be the old gas even though I used (fuel stabilizer when parking it), so I went to fill up to full (car had little less than half a tank when it sat).

Here are the things that the car is doing:
- Idles at 1.4k when stopped
- When driving and letting go off the accelerator the car jerks more than it should
- When on cruise control, speed up using the button on the steer wheel works fine, but when dropping speed the car again jerks after it drops the speed
- When the car is moving if I clutch in to let the car roll and leave the car in gear the RPM jump around between 1.2k to 2k until the car comes to a complete stop. I made a video of this, and when it's doing this my foot is no where near the accelerator pedal. (video: )
- If I do the same thing as above, but put the car into neutral instead of leaving it in gear while pressing the clutch pedal the car just goes to it's "regular" RPM (video: )
- There is no CEL on now. However it did come on right before I did the reset below, and it turned it off and it did not come back (yet?).

I've searched around and found a bunch of threads of car idling high, but it was after cleaning throttle bodies. I have not done this. In fact I have not done anything which is why it's strange since the car just sat.

The only thing I tried to do so far is getting fresh gas as mentioned above, and I also tried doing the ECU reset procedure using pedals, which brought down the idling RPM to 1-1.1k which is still high and the car still did all the other weird things. Also, that only lasted for a bit, and the car is back to idling at 1.4k RPM.

Any idea what this could be? I'm moving from Cleveland, to Denver in 5 weeks and I'll be flying back to get this card and driving it over there as a little road-trip, and would love to get this fixed before that time since I will have no tools or anywhere to work on the car in Denver being in an apartment.

Thank you

 

So I tried disconnecting the battery for 4 hours, then doing the Accelerator Pedal Released Position Learning and Throttle Valve Closed Position Learning procedures and it seemed like it had worked.RPM at idle after this were at around 736 when I checked with an OBDII scanner. Still a little high though since they should be around 650 +/- 50

However driving the car again today it's back to idling high. CEL came back on as well and it's P0507 as I figured.

I made an appointment at at Infiniti dealer, but I don't want to get ripped off as it seems to happen when others went in with high idle issues. I'm hoping them doing resetting with their own diagnostic tools fixes it, but I'm afraid they will try to get me to get a new throttle body or something.

Any suggestions?

 

Went to the dealer and they fixed it for $149.99 by performing the idle air volume learn procedure. Didn't seem to do it when I tried, but my guess is they used Nissan Consult.