D16Y8, Manual Trans.

It used to idle (when warm) at EXACTLY 800rpm. Not even a slight variance .. 800 always. All of a sudden last night, I was sitting in the driveway, and the idle dropped to about 700rpm. From that point on, it's been idling lower, and much more erratically. If I press the brake, turn on the fan or headlights, etc, the idle drops down to ~500-600 (then sometimes works its way back up to 7 or 800). Sometimes it stays put at 800, sometimes it dips back down to 500. (And I know, Civic's have a small alternator, it always did drop when you turn the lights on, but never down that low, and it always came back and idled at 800). It hasn't stalled yet .. but at 500rpm it feels pretty close. 200rpm may not seem like a lot .. but trust me, it's not idling right.

I do not think it's a compression issue, or that I've lost a cylinder (there's no lope .. the idle is smooth, just low). It's not spark plugs or a clogged air filter (just replaced both).

Seems like an electrical problem to me. Alternator? Anyone have any thoughts?

 

well mines always done that. you can actually play with the idle just by pressing on the brake lights.
i got my car used last year so i coudln't tell if thats normal or not.
mines a d15b7 i think manual

 

I know it normally does that to some extent, but what I said in my post was that it has gotten worse. It has NEVER dropped down and idled at 500rpm (on the verge of stalling) before, no matter how hard you press the brake. So no .. it's not normal.

 

Go through the normal maintenance things (plugs, fuel, valves...). You have to do them eventually so might as well now when there's a problem and you're not quite sure what it is.

If you've done all of that and it still does it, try taking the car to an AutoZone or something and have them test the alt. They can do it while it's still in the car and it's FREE. :thumbup:

That's what I would do.

 

i second that motion......:thumbup:

 

Good call. I've already done the plugs, and I replaced the air filter (thought it could be clogged). Neither helped. I really think it's either the alternator, or it's possibly out of tune...?

If it helps, this happened very suddenly. As I said, I was sitting in the driveway with the car idling, and it was fine. Then all of a sudden the idle just dropped, and it hasn't been the same since. Does that shed any light on anything?

 

Head to AutoZone and test the alt.

 

If it's a Civic manufactured in 96-97, there's a common problem with some of the alternators. The cars in question have alternators that have a weak output. It's not in any service bulletin, but after seeing reports of this on the web, I called my dealer, and they said they were aware of the problem, and it could be taken care of under warranty. Luckily for me, this was a month before my warranty was up. Before I had Honda replace the alternator, my headlights would sometimes dim at night, especially when I turned on the fan(heater/ac) or when I unlocked the doors or rolled the windows down(pretty much anything that uses electrical current). This always bothered me because I don't have any kind of car audio, or anything else that would sap current like that. After I got the alt replaced, everything was gravy. Have the output of your alternator checked. If it's low and you're still under warranty, have Honda replace it. If you're out of warranty, I have a spare alternator off my spare Y8 block(from a 99 EX, check sig).

 

It's a 97 .. and I've definitely noticed all that before. The headlights & guage lights dimming when you turn on the fan, etc.. It's doing just about the exact same thing now, except that it's gotten way worse. It's really killing the idle (down to ~500, and almost stalling the car). So yeah, you're probably right .. that's what makes me suspect the alternator. (It's feeling sluggish up to ~3000rpm lately, too, esp in the cold .. could this have anything to do with the alt?)

Unfortunately it is out of warranty. I really appreciate the offer .. but I'm in Canada, so with shipping/duties/whatever, it's prolly cheaper for me to just buy a new alternator up here.

 

check your EACV and clean it.