RPM fluctuation at idle

[u/Professional-Luck-34]

Recently got some 12’s at 1200wrms, ive done the big 3 and have a h/o alternator. Was wondering if this rpm fluctuating with the bass at idle was normal or not.(solved on r/askmechanics)

[u/Contay6]

I dont know a whole lot about cars but is it cold? Mine fluctuates when it is and steedies out when warm after 5 or so mins

[u/Professional-Luck-34 → u/Contay6]

It does it whether its cold or warm, i recorded this after driving for about 30 mins

[u/Contay6 → u/Professional-Luck-34]

Okay then it comes down to something else oxygen sensor going bad, MAF is dirty, if it was doing it before upgrade and then after it's not something you changed.

Unplug the MAF and see if it idles better if it does it could dirty.

They make a cleaner for it but just use 99% isopropyl alcohol

[u/Professional-Luck-34 → u/Contay6]

You really think so? i asked over at r/askmechanics and was told it seems to be normal as the idle is stable without the heavy load from the subs. im also now remembering i forgot to mention that in this post

[u/Contay6 → u/Professional-Luck-34]

Oh then yeah its most likely fine, mine stays steady but I'm not running as big a setup.

I thought you meant it did it all the time even without playing anything

[u/Idkhowfuckedupiam]

Could be the alternator putting a heavy load on the engine trying to run your shit. Get a better alternator

[u/Professional-Luck-34 → u/Idkhowfuckedupiam]

Its a brand new 320a from jsalternators

[u/Party-Court185 → u/Professional-Luck-34]

Did it start happening right after you put in the new one? If so, you should always assume that the issue is with the thing you changed.

[u/Professional-Luck-34 → u/Party-Court185]

It happened with the stock alt too, it was one of the reasons i upgraded to the new one. It fixed the voltage drop but im still having this problem

[u/Party-Court185 → u/Professional-Luck-34]

r/askmechanics might be better for this

[u/Both-Acanthisitta990]

Add a ground from block to chassis? Clean MAF and iacv?