bdazzled

2000 Civic LX D16Y7: I started my 120K service routine yesterday, including new spark plugs. Driving around this morning, after the engine had warmed up, the idle now drops nearly to ~50rpm and shudders when I come to a stop. It hasn't stalled, but feels like it might. Other than that, it starts fine, and runs strong and smooth at speed.

I replaced the old plugs (gap was up to ~.065) with new NGK ZFR5F-11s (gapped to ~.042 out of the box.) I've changed the plugs before, without incident, and the plugs were the only thing I touched yesterday. Can anyone point me toward a solution here?

Former User

Did you reset the ECU or disconnect the battery?

bdazzled

Yes, I disconnected the neg. battery cable before changing the plugs and reconnected it afterward.

Former User

You reset the ECU, which is now in relearn mode where the idle can be a little rough for a short time.

bdazzled

Well that makes sense. And is a huge relief as well. I'll just keep driving it then.

Thanks for your help.

JayStarr22

I'm having a similar issue with my 99 civic D16Y8 auto trans.
It randomly died about a month ago and wouldn't start back up. I changed the spark plugs, wires, cap and rotor. Still wouldn't start.
I finally tested and replaced the coil with a cheap one online, it was neither tac or hitachi, some off brand i assume.
It stared up fine,but a week later it started idling low and dying. I presumed it was the off brand coil, So i payed more and got one for a tec which i have.
Again it worked fine for about a week and then stated idling low (200-300rpm)
So i found the idle stop and brought it to a nice 900rpm idle.
Now when i start it in the morning the idle starts around 2500rpm and stays the until it is fully warmed up, Then it goes back to almost dying at low idle.
No over heating and the engine runs stronger than it did when we first got the car.

Is there an air fuel mixture screw somewhere? our do i just need to re-adjust the idle screw and hope the ECU just needs to re-learn again?
Is it passable i need to replace the ECU?

I have disconnected the battery a few times threw all the replacements, and again about a week our two ago. I also have a p0420 o2 sensor cel light on, but it was on well before all of this, and when i had the off brand coil in it had a crank shaft position sensor cel light on, but that went away with the new coil.

HondaPartsHero

NEVER mess with the idle stop, ever. Check the FAQ for an idle set how to.