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Rough Idle Solution - Idle Relearn

jersail

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I have a stock 2016 Civic EX-T, and have had an issue for several months where the car idles at about 600rpm and feels very rough while in gear with the A/C turned off (at a red light, for example.) I've researched it on this forum (there are lots of threads on this topic) and couldn't find any real solution, so I finally brought it into the dealer today. They agreed there was an issue, and ended up keeping the car for a full day but couldn't find anything wrong. Eventually they decided to do an "idle relearn," and I was skeptical, but it actually seems to have resolved the issue ($155 later!) I had to replace the battery last Spring, and the dealer says that could have messed with the ECU in some way.

Now the obvious issue is, what happens if I need to disconnect or replace the battery again? Does anyone have any information about how to perform an idle relearn on these cars without bringing it back to the dealer, maybe from a service manual? There is some information online but it is inconsistent and I'd love to hear it from some reliable source.
 

zspeed

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What we did for the 7th gen Civics and the 2nd gen CRVs was to disconnect the battery for about 5 mins then hook it up again. Start the engine and just let it run again for a good 5-10 mins for the ECU to do its adjustments.

No idea if that will work with the 10th gen Civics.
 

calonzo

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Now the obvious issue is, what happens if I need to disconnect or replace the battery again? Does anyone have any information about how to perform an idle relearn on these cars without bringing it back to the dealer, maybe from a service manual? There is some information online but it is inconsistent and I'd love to hear it from some reliable source.
I don't know about performing an idle re-learn, but you can avoid that by using an external 12V power source to maintain power while switching out the battery.
 

DRUSA

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There is an idle relearn and a ckp sensor relearn when it comes to idle issues. The idle-relearn can be completed by disconnecting the battery for about 10min and then allowing the car to idle with no loads (no a/c on, no radio, no headlights etc) until the cooling fans cycle twice. A CKP sensor relearn is the crank position sensor "zero" location relearn. This must be performed with the Honda HDS scan tool, but it will allow the computer to relearn where TDC is. This helps with engines that have higher mileage as the computer will compensate for timing chain wear etc and learn "true tdc" again. Helps with misfires and other random engine issues.

The VSA/ABS light will usually be on after a battery disconnect, don't worry, drive the car above 8mph in a straight line and it will clear by itself. The system needs to relearn again by driving.
 

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