Hi guys. I have an 08 g37 5at and ive recently had this problem where when im driving and let go of the throttle the rpms drop below 500 then jump back up and the car lurches forward. It does it in pretty much every gear but more aggressive in lower gears. Also it doesnt do it when cold seems to get worse the hotter the car is. Any help please. I have a video link below of the issue. Thanks
https://youtube.com/shorts/oL9dIik1WhM?feature=share

 

Does the "jump" happen under braking? Also, how is your base idle- steady at 650rpm or does it settle higher?

 

No braking involved. The drop and the jump happens right after the throttle is released. My idle is at 750 sometimes 800rpm. I'm tuned with uprev also do idk if my tuner has set the rpm higher.

 

I know some 2008/09's had idle issues where the idle would jump and the car would lunge. Infiniti released a technical bulletin to have the ECU relfashed. Being you are tuned this obviously would not apply.

 

could a vacuum leak cause this? I'm suspecting i have one but haven't got it checked. I have this weird stutter at 2k rpm too, almost like a misfire but no codes or CEL

 

Yes, a vacuum leak can cause all sorts of engine performance issues. Same with intake air. Wouldn't hurt to make sure everything is clean and tight.

 

Alright ill get a vacuum leak test done. Also the rpm surging i believe (cant remember 100%) started happening after i cleaned trottle bodies and maf sensor. Ive done the idle air volume reset and all the other procedures but i dont think any of that made any difference. Also when i put the car in D it feels like its acceleraring more than it should, sometimes it even changes to second gear without me touching the accelerator pedal at all.

 

Being that these symptoms arose just after you did some maintenance leads me to believe the issue lies somewhere in your work. I would double check everything you worked on and make sure all of the intake/vacuum/PCV hoses are secure and the clamps tight. Also, did you make sure the o-rings in the TB's were properly aligned and the bolts tight? Probably wouldn't hurt to repeat the IAVL reset as well.

I had all of those symptoms- including the unintended acceleration- and the TSB solved those issues for me. Being tuned, maybe your tuner has some input?

 

Check for any exhaust leaks, especially around test pipes if you have any.

 

i do have test pipes yes. Im gonna get both a vacuum leak and an exhaust leak test done.

 

any update ?