I’ve been experiencing terrible idle fluctuation, Only happens when in park. If it’s in drive it’s normal even when stopped at a red light. I got a 2010 6speed auto, 2k miles on a reman engine, changed out spark plugs and coils as I thought it could be a misfire, helped a bit. Got a PO101 code, so I tried cleaning MAF sensor, no go, bought new MAF sensor and still nothing. Only mods that I think could affect RPM fluctuation is my AEM CAI and my midpipe/catback, but I’ve had them for some time now and never experienced anything out of the ordinary. Also need to mention that there’s no vacuum leak that I’m aware of If anyone could point me in the right direction that would be much appreciated, thank you all!

 

Is the P0101 code still showing? Does it take time to come back once reset?

What are you fuel trims while idling and warm? What about MAF rate g/sec?

 

+1 and did you change the o-ring when you replaced the Maf?
I've personally had terrible luck with that O-ring. Every time I take the Maf out to clean it the o-ring will not does not ever never for me fit correctly back in the Maf housing.
And I'm not doing anything directly to the O-ring, I leave on the Maf and it does not like to fit nicely back in to the maf housing.

So if you're still getting a P0101 you might want to have a look and make sure that Maf O-ring is fitting correctly.
Just another easy free thing to check.

 

I have no idea what my fuel trims were as I didn’t know how to check it out lol but what I did do and it’s working for me so far (fingers crossed it stays that way!) is I reset the fuel trims by smashing in the brake pedal 20 times and disconnected the battery for about 30 seconds for good measure, started up fine and idled perfectly, no more wonky idle fluctuation. I hope that’s the end of it

update: i ******* lied LOL resetting the fuel trims didn’t work. After 2 drives the idle fluctuation came back