Rep Power: 0

My 2001 Civic LX coupe is having an extremely odd problem somewhere in the electrical system. Symptoms:

1) Battery Light Flicker -- every now and then, the battery light flickers on, just for an instant. There is no consistency to when it does this. Sometimes it will do it when I first touch the gas pedal, even before the engine responds. Sometimes it happens after I let up on the gas and let the engine coast down, as when approaching a traffic light. In all cases it's a single flash of the light, then it goes out again and stays out.

2) Engine Running Rough -- When the car is idling, the engine runs smooth for a while, then runs rough for a few seconds, then smooths out again. It runs rougher when it's hot (been running for a while) than right after I start it. The roughness feels like a sag in the rpms, or perhaps a cylinder misfiring, but I am not sharp-eared enough to tell which.

3) A/C Buzz (possibly unrelated) -- There's an audible burring noise from under the hood which goes away if I turn the A/C on, and comes back when I turn the A/C off. The A/C itself is working fine.

The alternator in the car is new -- well, not _new_ new, but a remanufactured one that was put in just a few days ago by the shop I use, as a warranty replacement. (They replaced the original alternator after it died last May.) The new alternator did not fix the problem I'm talking about. I took it back to the shop again and talked to a tech there about it. I've also talked to another mechanic I know and trust. They've given me two different diagnoses:

a) The shop tech says the alternator is fine. The problem is with my A/C compressor. It shares the alternator belt, and its bearing is grabbing every now and then, making the alternator belt slip for an instant. That causes the battery light flicker. The engine's load fluctuates rapidly as it tries to turn the alternator belt, which mucks up the engine rhythm. (His description was a lot more technical, of course; I'm paraphrasing from what I remember.)

b) My mechanic friend says the alternator is not fine. Specifically, the voltage regulator module inside the alternator is bad. AIUI, for a Honda alternator, the regulator MUST be from a specific manufacturer. If the regulator comes from anybody else, you can get this exact problem: flickering battery light and rough engine.

Who's right? Anybody here have any insight to offer?

-- Jon

 
Rep Power: 314

This happens when you use an aftermarket non OEM alternator. So, even though the alternator is "Fine" it's not functioning correctly. I suggest you get an OEM. The engine running rough just sounds like you need to clean your IACV.

 
Rep Power: 0

When I had my flickering lights problem, long story short the perfectly good alternator was actually overvoltage and the ELD or something kept bouncing in and out of low power causing the lights to flicker pretty bad.

There is merit to non OEM altenator appearing to be fine but I suppose the ELD could create a little havoc if it can't talk to a OEM voltage regulator.. Not entirely sure how that part of the electrical system works though.

As for the running rough thing. Could be electrical, loose ground.. Though I did have a car that a similar issue of smooth cold, rought on warm up and then randomly smooth and rough.. First time it did that it was a knock sensor that was corroded.. Second time it was a failing O2 sensor.. The 02 sensor failure took weeks before it thru a check engine code.

AC Buzz.. again previous car my AC clutch would make all kinds of noise but when the AC was engaged noise would go away. Not sure how the vic AC works but might just have some dirt up in the clutch mechanism or a bad AC clutch.

Good luck and let us know what you find out.

 
Rep Power: 0

The story so far:

1) Replacing the alternator with a Honda one (as in, obtained from a local Honda dealer parts department) seems to have eliminated the charge-light flicker. At least, it hasn't come back in the two weeks since the new alternator was installed.

2) The new alternator did not fix the idle stutter. Last week I got new spark plugs (the same model Honda uses), cleaned the throttle body and put a 5-oz bottle of "Lucas Upper Cylinder Lubricant and Engine Cleaner" into the gas tank. This has enormously reduced but not quite eliminated the idle stutter. Where before the engine was running rough for five or six seconds at a time, and sometimes choking so badly it felt like it might stall, now it simply coughs for a coupe of seconds, then smooths out again. As before, this never happens when the engine is cold, only when I've been driving for a while. The most reliable way to reproduce it seems to be: drive on the highway for a while, get off at an exit ramp and stop at a traffic light at the end of said ramp.

Any further thoughts or suggestions?

 
Rep Power: 813

if car is shaking badly, it could be a misfire and not just a rough idle. what brand of plugs did you get? you may also have some blockage in the injectors. may also want to clean out the IAC idle valve on the throttle body just to rule out any idle system issues.

 
Rep Power: 248

Ok, I am having a similar problem. I have read many discussions about this on a forum that my shop is part of. This site is where shops across the country post problems and fixes. The problem i am having is rolling idle, where my idle fluctuates 500 rpms. my battery light is on even though i am charging at 14 volts. my check engine light is on but with no codes, and no data stream and after a few minutes of idling my dash shuts off. my cat is shooting flames about 4 inches past my cat. so i was reading and there were over 50 articles with the exact same problem. the fix was replacing the PCM. Honda has a bulletin saying that after an alternator replacement a voltage spike may take out the PCM and cause it to go bad and cause various electrical problems. This might be the same problem your having. Also anyone know where i can get a PCM for cheap

 
Rep Power: 0

Returning to update this thread.

First, my thanks for the advice I got.

Second, a bit of necessary background: back in January, a local shop (the same one that had so much trouble with the alternator) replaced all four spark plugs and two of four ignition coils. One of the coils failed overnight, and when I started the car the next morning I got a flashing Check Engine light and the engine was missing so badly the whole car was shaking.

The plugs they used were 'the same as' original, but not exactly the same. My mechanic friend bought four of the exact same model plug that Honda uses and installed them. This made no difference to the rough idle problem. He and I then pulled the fuel pump and checked it. The fuel filter looked clean but was gritty to the touch; the pressure was fine. I have been adding a dose of the Lucas cleaner stuff with every tank of gas, and it seemed to be slowly getting better.

Until this morning. We had a sharp cold snap the last couple of days, with nighttime lows in the high 30s, daytime highs in the 40s. Yesterday I drove the car a round trip of about 120 miles - 60 out, 60 back, with several hours in between. It drove the same as it's been going for the last couple of weeks: occasional stutter at idle, but not as bad as it was several weeks ago.

This morning, I started out to go somewhere and inside five minutes had serious problems. The Check Engine light is flashing, and at least one cylinder is misfiring so badly that the whole car shakes at idling and at low speeds. Just like when the ignition coil failed back in January. Have I had a bad coil pack that sort-of worked as long as the weather was decent, but the cold snap killed it? Or is it likely something else?

 
Rep Power: 813

hmm ignition coils are very hard to break unless there is another problem. you may want to check the charging system and make sure the alternator isnt putting out over 14v, which could damage alot of electrical parts. did you use ngk or denso spark plugs? any other brand will not work right. you can test the resistance of each coil pack with a multimeter and compare the ohm readings. they should all be very close to the same ohm reading.