Okay now, the plot thickens....

I bought four brand new 2004 s2000 coil packs from Autozone. They come in a Duralast box, but they are denso coils and the PN's match what OEM Honda is. According to everyone on here, 2004 coils work equally well in a 2002.

I installed said coil packs above.

I reset the ECU using the fuse-pull method.

I fired up the car - no CEL initially, no flashing, and the car sounded like it did before the failed Cyl 1 coil. Thus, it's conclusive that one of my coils was indeed bad. I felt good!

HOWEVER...

I ran the car for a bit to let the computer learn the idle (3000 RPM method for a few minutes). During this process, I could hear light, muffled pop sounds from the exhaust. The engine sounded good - again it sounded like it did before the failed coil. However after about a minute of this, the CEL came on and I pulled a misfire code on Cyl 1 and Cyl 2.

I reset the CEL again, and drove a couple miles to fill up. Drove there/back and the CEL did not come back on this time. It remains off right now.

THIS MAY BE IMPORTANT - Something I noticed that was peculiar... every time I heard one of those light muffled pop sounds from the exhaust, my gauge cluster lights would slightly dim. I tested this theory by revving the engine up/down, and every time the exhaust popped slightly, the dash lights dimmed briefly corresponding with each pop. If the pops are engine misfires, I suppose it would make sense that the dash lights would dim as it would put more strain on the electrical system? Just food for thought... or maybe a clue.

The CEL only came on when the car was under no load. When I drove it to the gas station, the transmission was engaged, and at that point I couldn't hear if the exhaust was still popping. My dash lights however did not dim at all, making me think that when the car is under load and being driven, that the misfiring is not occurring.

The only conclusion that I can draw at this point is that there are multiple issues going on. Billman, it would be much appreciated if you could chime in since there is zero reference to go off of on the forums at this point. Also anyone else that knows where to go from here - please, please help!

The ONLY forum post I found that may be slightly related is this one: https://www.s2ki.com/s2000/topic/895678-shaky-idle/ as my car has done this since the day I bought it.

Also I still have not had my fuel injectors cleaned... maybe they're the culprit and I'm running myself in circles because one of my coils HAPPENED to fail and make me think that it was bad coils all along?

Thank you all.

PS - after I changed the coils to the new ones, the CEL never started flashing again. It just set with Cyl 1 and Cyl 2 misfire codes.

 

Please do a leak down. Chances are you have some valves that aren't sealing 100% anymore given your milage. Injectors COULD be causing it and there is a member on here (Wadzii) that services injectors at his place of business. PM him.

 

Tight valves can cause that type of idle misfire, because when engine speeds are low you don't have much valve overlap, it won't do it when the car is moving because engine speed insures more overlap.

When your car idles and you hold your hand to it, is the exhaust warm or hot, or is it kind of cool?

 

Should I put my hand on the exhaust at the back of my car?

 

Not the actual exhaust, the gas that comes out the tail pipe, is it warm or is it kind of cool?

 

I'm really curious what your issue is because I am having what seems to be the same exact problem.

My Thread

Right now, mine is running but it's not running perfect. At low RPMs I can hear it missing. I don't smell gas and I am not getting any codes whatsoever.

Also, your dash light flicker/dim is due to the alternator. Technically it's a part of the alternator (the rectifier). That's what I gather from this thread anyways.

Good luck and keep the updates coming.

 

Check your valve clearance!

 

I have a quick question on how the CEL works - when the car is misfiring, how many misses does it take to throw the light?

I figured it would do it immediately after one detected misfire. But now I don't think that's the case?

 

The CEL will only come on if the misfire affects something emissions related, if it's a tiny misfire it won't even register. First off it has to be bad enough that it causes a variation in engine speed. The crank angle sensor will pick up that speed difference and trigger a warning code first, then you'll get a CEL. You may not have a CEL but that doesn't mean that the computer hasn't stored a code. You would have to hook it up to a fancy scanner to see this, as the cheap scanners only pull up codes, but don't tell you how often or under what conditions. It won't trigger a CEL if you have incomplete combustion, as long as compression is 135 psi you'll get combustion, it will just be nice and smog rich, but nothing a catalytic converter can't handle.

Computer gives two rats if your engine is making maximum power, it just cares that all the emissions stuff is working. Usually a car that doesn't have emissions problems is running properly, but sometimes the computer just compensates for a bunch of stuff that although you notice it, the computer says, 'hey I'm holding down the fort over here, you can sit there and suffer for all I care'. I guess since this car has such little torque, any drivability concern is more noticed by the driver than if it was a torque monster V8. The average person that never floors the gas would never notice.

The knock sensor isn't pulling timing because it wants to save the engine, it does it so it doesn't burn the catalytic converter.

 

I've been using Torque (Android app) to check for CEL codes, so I'm guessing that doesn't count as a fancy scanner.

When I say the exhaust makes "pop" noises, they're so light that even recording it with a decent camera you won't be able to discern it - it's almost that it's not an actual misfire. I always assumed that a misfire makes a nasty running noise, which is what it did when one of my coil packs went bad. As far as engine power goes, it drives great - produces full power, revs to 9k (I max it out quite a bit, especially in the nice weather), shifts fine, doesn't lug, etc. It runs like a Honda s2000 engine should.

This is what brings me to not thinking it's a valve clearance issue. At the 105k interval, Honda Dealer adjusted the valves - they said they were all in spec except two exhaust ones (slightly tight). At 125k miles (about a year ago), I got my first ever CEL - random misfire. I pulled the valve cover, and my retainers were so badly cracked that they were maybe a few hundred miles from dropping a valve. When I put everything back together (with AP2 retainers) I was EXTREMELY meticulous with adjusting valve clearances. Cold engine (hadn't been started in two days) and I triple checked everything. I can't imagine that I screwed up so badly as to not get the valve clearances right on all four cylinders... I'd like to give myself a little bit of credit! I can definitely check them again tomorrow after the car has sat all night if you guys think it's worth the time.

I did feel my exhaust today like you requested - I can hold my hand about an inch away from the exhaust output at the back of the car at idle. Any closer and my hand starts to hurt/burn. The exhaust is definitely warm/hot. I assume that's right?

PS - I've driven about 100 miles after I reset the CEL from the last time (after I replaced the coils, I had a solid CEL after a few minutes, see previous post). It has not come back up since... this is EXACTLY what happened last time after I swapped out my retainers. I did the job, got a CEL random misfire, reset it, and it didn't come back for months. I kept tossing in injector cleaner and that *seemed* to keep it at bay.

I'm thinking maybe I should just bite the bullet and send my injectors off to the dude on here who cleans them? I just hate having more downtime for my baby For how cheap it is, I don't see why I shouldn't. In the mean time I can check my valves again, spark gap, fuel pressure, etc.