Here's the scenario:

Had CEL because of misfiring p301-p304

Replaced spark plugs but CEL came back

Did valve adjustment (Honda said they were tighter than specs) CEL gone but came back

Honda replaced ignition coils under emission warranty, CEL gone but few days later when I tap the gas the rpm drops to 200-300 rpms and the engine shakes like its going to stall but it goes back up to normal idle 600-800 rpms.

I don't have a CEL and when I used OBD2 scanner it found no codes.

Anyone experience this? Thanks.

 

mine does that when i first start it up. after that it doesnt though.

 

I had the same problem about a year ago. For some reason it was the Battery.. just bought a new one and the problem ended. Also the battery i replaced was 3+ years old.

 

Did you ever get weird CEL with your weak/bad battery?

 

This is likely just coincidence with your coil pack change. Just about every S2000 does this at one point or another. Mine does it several times a year at least. It's in large part due to temp or humidity changes. The ECU just gets "confused". This should go away within a few days. If it doesn't, then post back here and there could be something greater going on.

 

That's interesting that you mention the weather and humidity. I had this happen a few weeks back when the PM temperatures were dropping into the 40's. I know, I know...you guys are laughing but it was normally in the 60s to 70's before that. I was a bit concerned but it went away and hasn't done it since.

 

Maybe try a fuel injector cleaner? I just put in some of the techron fuel cleaner from Costco. It may be conicidence, but I havent gotten the low idle shakes to come back yet.

Plus the engine seems to rev more smoothly. I think I'll be putting in a bottle of this stuff in the fuel tank with every oil change.

 

I just had my 7500 mile maintenance and I believe they put fuel injector cleaner. But it still randomly idles low to a point it shakes for about a second.

 

all of my s2000's have done it. I wouldn't worry if it is only some of the time.

 

This was common for me after a year of ownership. I took it to the dealer last week to buy some OEM clips and talked with the S2000 expert here in our area of my old idle problem. He told me just clean your throttlebody and intake and you should be good to go. So while I was there I had him do it and since last week I have had no low idle (then back to normal idle) anymore. Just like new. Now I will see how long it will last.

He said it was very common and a common complaint thats easily fixed.