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I have a 1997 Civic that has been having intermittent problems that I’m not really sure what to do with. I’m not great with cars, but am confident enough to do some troubleshooting and handle simple repairs on my own. I’ll do my best to give a detailed description to what’s going on. I don’t drive my car often, so I kind of discovered these problems over a period of time. My check engine light is not on.

The initial problem was a rough idle when stopped at a light or when traveling at low speeds (<20 mph). Lately, this has been happening when traveling at higher speeds as well (up to about 40 mph). The rpm gauge fluctuates and, when moving, the speedometer occasionally drops to 0 mph and then jumps back up. Once or twice, the engine has stalled out due to the idle getting too low. When driving at night the rough idle is accompanied by flickering headlights and my CD player occasionally resetting (the display goes blank and then turns back on in 1-2 seconds). It seems like an electrical surge to me. Last night in my garage, I noticed that turning the AC on/off affects the surging as well. For example, with the AC off I was experiencing a rough idle and headlights flickering a little. When I turned the AC on while this was happening, the idle revved up and the headlights got brighter and then the engine stalled out and the battery died. Again, what happened could best be described as a surge of sorts.

As I mentioned, the rough idle and “surging” are intermittent. Last night, immediately after my car stalled out due to my turning on the AC, I restarted the engine and it ran smoothly. No rough idle, and no headlight flickering. However, when the engine is running “normally”, I’ve discovered that my battery light comes on, but only barely. During the day time it’s not noticeable, but when driving at night you can see that the battery light is barely on. My battery is less than a year old and I’ve never had to jump-start the car even though this has been happening for over a month. It’s almost like the alternator is working, but only partially…not even sure if that makes sense.

If anyone out there could offer some insight, I’d appreciate it.

 
Rep Power: 211

Not sure how to connect the rough idle with the numerous electrical problems. My first step would be to get the alternator and battery tested (autozone and advanced auto parts both do it for free). Though it's probably not a vacuum leak, try disconnecting your brake booster line while the car is idling (doesn't matter if the engine is warm or cold) and see if it stalls. The only other thing that I can think of that could be causing so many problems at once is a short somewhere in the electrical system. My initial gut instinct would be to check the main relay under the hood. Ensure vital connections are grounded correctly. Perhaps turn the car on and let it idle, and have someone watch under the hood of the car (while you're fiddling with the A/C/, etc) to see if anything abnormal happens or if you see sparking.

Hope that gives you some direction.

 
Rep Power: 234

Definitely have the alt checked. Low voltage can do weird things- even kill the ECU.

 
Rep Power: 0

I just cleaned the IACV since I figure that might be a cause for the rough idle. I'll bleed the cooling system another time. Maybe the electrical issues and rough idle are two separate problems and are not related at all?

Anyway, I'll have the Alternator checked and will go from there.

 
Rep Power: 0

Since I've cleaned the idle control valve about a week ago I haven't had any idling or "surging" problems.

Regarding the alternator/battery light, I tested the system and here are the readings:

Battery w/car off - 12 V
Car on - 14.2 V
Car on w/full AC - 13.7
Car on w/full AC + headlights - 13.4

Is it normal for the voltage across the battery terminals to drop when you start switching on different circuits in the car (AC, headlights, etc.)??

 
Rep Power: 234

^^ Yes

 
Rep Power: 0

I know this response is really late, but I figured I'd give an update just to close this loop.

Since I cleaned the idle control valve, I haven't had any idling issues, so that appears to be the culprit.

My battery light still comes on very dim whenever I drive the car, but my battery still hasn't died after several months of this happening. The voltage across the battery terminals seems to be okay, so I'm not exactly sure why this is happening. I'd like to resolve the issue, but since it doesn't appear to be affecting my car's performance, it's not a pressing matter.