On occasion (every couple weeks or so), my engine's speed starts bouncing up and down, perhaps a variation of 200-300 rpms, very consistently every couple seconds. It can suddenly begin while idling or while driving.

I first noticed this driving at night when all the interior and headlights kept getting stronger/weaker, and then noticed the engine performance was jumping to this rhythm as well. Only shutting the engine off for a little while seems to stop it, as it mysteriously returns back to normal after sitting turned off for a few hours or days.

While the engine is jumping, the voltage from the alternator seems to be jumping from 12.2-14.3-ish. I have been assuming this is a symptom of the problem rather than the problem...?

Another related or unrelated symptom is that the car has difficulty starting sometimes. Strong battery, but no ignition, and only letting the car sit for a few hours or more seems to allow it to start like new again, and run normally for the next week or two.

I don't get any dashboard trouble lights when experiencing issues, so where do I begin to troubleshoot this? I've never had anything weird like this happen before, and it seems to have started being an issue fairly suddenly.

Needless to say, my wife is scared to drive the car now.

 

I would start with checking your battery connections and your grounds. I'm not too certain where your main ecu ground is but I would take it off and clean the area it's bolted to as well as the ground itself. I've had issues before where my battery was going bad and it was actually emitting some battery fluid and it was corroding the positive post to the point that there was a white film that was blocking the post from giving a connection. See if that helps.

 

you could check your ignition switch also.if i recall there was a recall on those at one time.check your vin number with your local honda dealership.mine was bad/going bad and causing my car to do weird intermittent stuff as well.

 

I'll look into the ecu, thanks for the suggestion. I just replaced the battery, which I thought solved the problems, but now I'm wondering if the problems caused the demise of my battery. Lots of corrosion built up recently and it gave inconsistent voltage readings. Replacing it seemed to help, until the problems arose again. I had to replace the corroded post connector, something I spent a fair amount of time on, and am pretty certain the connections are excellent at this point.

Thanks for the tip. No ignition switch recall for this VIN according to ownerlink, but there is also no shortage of ignition switch problems with this year on cars that weren't covered by the recall. I'll investigate how to test this if a new one might be needed.

 

I never actually said to look at the ecu...i said "main ecu ground"...i'm talking about the ground that is attached to the engine that is used by the ecu as a ground.

 

As far as the undesired revving goes, I had the same problem with my 2000 Accord. What I did was a cleaned the idle air control valve and the problem stopped immediately.

 

My bad, thx for pointing out my ADD. That sounds simple to tackle and easily remove it from the list of potential culprits.

I may be biased but think that's an awesome first post. It looks like the iac valve is a common problem in these cars, and I found a pretty clear video for this engine to help clean it. (except for using "exhaust" where he means "intake" but I think that's an ESL issue and not ignorance, lol) Thanks much for the tip.

 

You're welcome man and thanks, I appreciate it. You may also want to clean the throttle body with some cleaner while you're at it. Good luck!