try the stabilizer

 

it happens at exact frequencys inside rpms, you probally have on or more bad motor/tranny mounts. I would investigate these for play.

 

The 1st thing I would do is change out the spark plugs. 90% of car running problems are just bad plugs. It's an easy and cheap fix.

 

I've got the same problem with my 96 EX. I too, recently changed the plugs, wires, cap, rotor, and had a valve adjustment done.

It was recommended to me to change the fuel filter, which was on the slate, just haven't gotten there yet. Might want to look at doing that too.

 

Well as stated, I just replaced my spark plugs less then 5,000km's ago, so not sure if they're the problem..

But I did have to replace one of my motor mounts (driverside) about 50,000km's ago, during my last tune-up. the other 3 mounts were fine then..

 

If you just replaced the plugs 5000 km ago, then it is unlikely to be spark plug related (Honda's maintenance schedule recommends changing the copper spark plugs in our cars every 48 000 km).

Even though motor mounts generally last a very long time, it might not be a bad idea to check them, especially since one already went out when your car had roughly 100 000 km. Have you looked at other parts of the ignition system, along with sensor inputs to your ECU? I have seen a faulty MAP sensor cause a rough idle (intermittent). Good luck to you.

 

could be bad sensor ground also, btw how was your motor mounts?

 

hmm some new updateds on the rough idle. When the rough idle happens, I can hear the car's fan turn on, and when it goes off, the rough idle stops..

How would I know if the other mounts have gone bad? I know what the driverside mount looks like, my old one was cracked. I'm not sure where the other 3 motor mounts are tho.

 

Well I doubt my problem relates since you have traced it to the fan turning on and off, but I had a bad vibration at certain resonant frequencies and I had a bad gasket in my exhaust line. Vibrated and sounded like crap, took it to the muffler shop and they fixed it up.