So i just got my car back from the shop today, i sent it back to the shop due to me wanting to figure out why my Rpms were dropping to 3-400 then rising back to 800 then finally going back to idle around 600 all in the matter of 4-5 seconds only when I come to a stop and or idle…it’ll do it frequently if I’m at idle in Park or in Drive. The shop told me that it was the alternator loosing voltage going from 14.5 down to 9.5 and that what was causing the rpms to drop and rise when the alternator lose the voltage and regained it. They replaced it, cool driving home and it seemed fine for the first 4 miles no issue then I come to a stop sign and boom! it drops in rpms then back up and down back to req idle. So clearly that really wasn’t the problem so I’m wondering if anyone can help me troubleshoot this? I have aftermarket long tube cold air intakes from stiller and a cat back exhaust system. But the rpm issue has been before the intakes and honestly idk about before the exhaust… so I’m wondering if I’ll just need an ecm reflash or a tune and it’ll be the solution? Any thoughts..?

 

Vacuum leak past the throttle bodies, air leak past MAF sensor but before throttle bodies, bad MAF sensor, cracked intake manifold, PCV tubes cracked, EVAP system issue and few more.
I've experimented with intake pipes on my 07 and the MAFs didn't like any of them except stock. A tune will probably fix that but that's over $500..

-This is why i always ask for ECM fault codes..

 

sweet thanks, I can check it out this weekend when I have time. I’ve read other threads and others had the same issue with the rpms and it seemed like the TB were an issue bc they were dirty and had buildup. So I might try that bc I didn’t clean them when I installed the intake about a month ago.

 

Find the right video on uTube and once you clean them the right way, do the relearn process and should be fine. If not, then you need to find the air leak.

 

I did just get my alternator replaced at a shop along with a new battery the alternator is an OEM part and it didn’t seem to fix the problem… so that’s why I think it’s the TB or maybe the MAF sensors. But I can check out if it is a vacuum leak.
any YT suggested vid to clean the TB?

 

I'm sure plenty will shine on my comment but my 07 V36 no matter what i try, i cannot get the Idle Relearn process to work. I've tried 370z, g35/37 methods, timed with my phone to the videos, i even tried with Consult 3+ and that didn't finish after 10 minutes of starting the process. Exhaust cam phaser relearn works and throttle position but not the idle. Mine sits at 675-700 without AC on and AC on is 700-725. Get MAF cleaner and clean the MAFs and filters (if you cannot see the sun through your air filter, then it needs cleaning/replacing).
There are too many uTube videos to list, just search, scroll and watch; The more you watch, the better you'll be off.

 

yeah mine use to idle around 800 until yesterday since I got the alternator replaced it sits about 600 now but still haves the rpm fluctuating issue and the lights fluctuating aswell. I have the stolen gen 3 long tube intakes so idk if I’ll be able to see through them their the oiled ones not dry filter. But I’ll get the maf and TB clean this weekend any get back with you thanks.