I have a '99 Civic SI ... stock engine/head as far as I know.
I've had misfire issues in the past with this car, haven't owned it for that long, starting to think I bought a bad car ... but before I had misfire issues to the fact you could feel it, so read about the car having a weak ignition coil I went and bought a MSD ignition cap, rotor, and external coil ... after those changes the car was fine for a few months then it came back, bought new spark plugs and spark plug wires, problem went away again. Now it's back again and with a vengeance, this time it's a lot different.
Here are the current symptoms that started as of three weeks ago: rough idle, while idling the CEL will flash, the code reader device says its a misfire, and each time checked and cleared its in a different cylinder.
I cannot feel a misfire, but I can feel the rough idle. But the CEL will only flash after the car has warmed up when idling, during this time the RPMs will stay around 800, it will sometimes drop and raise a little bit. Turning on/off headlights will cause the RPMs to drop a bit before going back up, almost to the point of it stalling out (the car starts to shake when the RPMs get too low during this time)
The fuel filter has been changed, and it has pressure going through it.
The spark plug wires have been checked one by one, and keep checking them just in case, I forget which brand I bought but they are much thicker compared to the previous ones in the car.
Because there is a spark I'm to the conclusion that this isn't an ignition problem. I even bought a ignition module a few days ago and replaced it today and it made no difference.
Today also the car wouldn't start, it was acting like it was flooding, had to give it gas while turning on the car to get it to start. Also today cleaned out the throttle body, no luck.
So I'm at a dead end, I'm trying to do everything I can before taking it to an mechanic (don't trust the local or big business ones around here), so does anyone have any clue? I've read posts on here talking about cleaning out the valves, which have been done, or checking the spark plugs, which are still new. Any help is appreciated, and I will keep this post up to date if anything happens.
After changing the distributor the problem has been fixed.
UPDATE 2 (2011/3/4):
Everything is back, refer to my post at the end of this thread to see.
Last edited by firejackal; 01-03-2011 at 04:13 AM. Reason: Update on the problem.