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      02-10-2019, 07:02 PM   #1
8k_v8
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Strange idle issue after battery replacement

Hey All,

I recently replaced my battery for the first time since I've owned the car(2+yrs) and immediately started experiencing a fluctuating idle when coming to a complete stop.
I'll try my best to describe the issue, and appreciate any suggestions, as I have been unable to find anyone on here experiencing the same issue.



-Idle has a subtle fluctuation/step once I bring the car to a complete stop. Moving from:

700 to 600 then stopping at the 500 mark (never dipping below 500).


- Car seems to hold the normal idle until about a second after coming to a stop, then begins this "step" down to 500.


-Idle then goes back to "normal" with the clutch pushed in 750-850 range.


-It has been consistently doing this, with no wild fluctuations, or any improvement over time. The car hasn't stalled either.


-Idle doesn't change when I fill up so I don't think its the breather valve.


-I took the car to an indy to register the battery after install and mentioned the idle fluctuation and he said it was normal and okay to have it running like this but I could tell after a few days of driving it that something isn't right.
The car hasn't thrown any codes either. I just wanted to see if anyone had experienced this. Any tips are greatly appreciated.
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      02-10-2019, 07:30 PM   #2
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I recently began experiencing something similar (but with my DCT car). A cleaning of the very dirty butterfly valve of the idle control valve took care of the issue in my case. Follow this DIY from DATM3, but leave the ICV installed, remove the rear connecting hose, inspect, clean and reassemble if you want to give it a try. If you look carefully in this photo, you can see part of the butterfly valve inside the metal connection point at the top of this ICV (rear if installed in the car). You can also see the some carbon build up as well.


Image borrowed from DATM3's DIY here.
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      02-15-2019, 09:31 PM   #3
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Quote:
Originally Posted by Theodore View Post
I recently began experiencing something similar (but with my DCT car). A cleaning of the very dirty butterfly valve of the idle control valve took care of the issue in my case. Follow this DIY from DATM3, but leave the ICV installed, remove the rear connecting hose, inspect, clean and reassemble if you want to give it a try. If you look carefully in this photo, you can see part of the butterfly valve inside the metal connection point at the top of this ICV (rear if installed in the car). You can also see the some carbon build up as well.


Image borrowed from DATM3's DIY here.
Really appreciate the help! I'll be replacing my thermostat next week, so I'll clean the ICV hose while I have the plenum off and see if that helps. Thanks again
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      02-16-2019, 01:29 PM   #4
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Mine runs the exact same way and I am pretty sure that is normal. Your idle should only be 650-750 range when your fan/AC is running. When my AC isnt on Idle right around 500-550, as soon as I push my clutch in it'll pop up to 650-750. The idle without the AC on is a little rougher, but never stalled and it's been running this way since I've stopped using the AC(september?)

https://www.m3post.com/forums/showthread.php?t=1083506
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      03-01-2019, 02:57 AM   #5
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Mine does the same after replacing a faulty IBS connecting cable without battery replacement.
It idles lower now and randomly revs up to about 800 at the stoplight (without touching anything), then goes back to ~550. Clutch in makes it go up too.
I cleaned my ICV this summer so I don't thihk that's the cause. The idle is very stable, no fluctuations.
Should I reset battery adaptations after I have installed a new IBS cable which got rid of IBS fault codes?

On a side note, with Vibra technics engine mounts the vibration is much more pronounced now when the idle dropped to 550 (before I was usually at about 700).
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