Al_NFR

thanks for the advice @Gregg Lee! but yeah i tried it on both soft and hard mode but still no luck, still being limited to just 8.4k . i think I'm going to try and diagnose the fuel system, such as the fuel pump, filter, and injectors @Supercharged k20. can spark plugs be a culprit of this as well? not sure if they have ever been changed out. oh and is it normal when driving while you are in gear and just drop it to neutral to a stop, for the rpm to drop to 1k, then jumps up to about 1.5-2k then back down to 1k at idle? if not then I'm guessing some sort of sensor can be the cause of the rpm jump and not being able to reach 9k redline. thanks!

Kenshyn

Very common "issue" with AP1 as far as I know. My 2001 with 120k on it does the same thing. The RPM's only drop to 500 or so on a warm start. Cold start is 2000 idle and then slowly drops and warm idles at ~900-1000. My car has always done that for the four years I've owned it; I've never seen it as a problem, rather just a quirk of the car; it adds character
This should only be a problem if the car starts to die when coming to a stop. If it's not broke, don't fix it

As for the rev limiter issue...how certain are you that it's an AP1 motor and ECU? A re-tuned AP2 will redline at 8.4k
Like others have suggested, take some photos and/or video.

Gregg Lee

If idle is irregular you could try "rebooting" the ECU by disconnecting the battery for a while. Has worked for me.

Re rev limit, AP2 ECU had occurred to me, too. If engine runs well without hesitation up to 8400 then seems to hit rev limiter, AP2 ECU seems like something to check. Other possible things you listed seem more likely to affect it all the time, not just at 8400.

You might save yourself a lot of searching by getting diagnostic check done.

Al_NFR

Yeah i just looked at the block and head both stamped f20, and the ecu is for an ap1. I called Evasive Motorsports and they said it can either be spark plugs or it might need a valve adjustment. Just checked te spark plugs the gap on them are still good, a lot of carbon build up and just look old so ima just replace them. Guess ima look into a valve adjustment soon, i dont hear any ticking of any sort so im kinda iffy about doing it, but it wont hurt i suppose. Ill keep you guys updated on this issue. And thanks again for all of the advice you guys have been giving me, its greatly appreciated! Ima try to upload the video i took today tomorrow

Gregg Lee

Valve adjustment and plugs make no sense for what you have described. They would not produce an abrupt rev limit effect always at the same rpm.

Last try:

Will the car go past 8400 going down a steep hill? If not then really sounds like a spark or fuel cut rev limiter operating rather than weak engine or something dragging.

Find someone familiar with how an S2000 should run, and have him/her drive yours. Or you drive his/hers to compare.

Mis-timed cam would detune engine. So would retarded timing. Retarded timing could be caused by a bad knock sensor.

But you can waste a lot of time guessing at causes though, which is really all we are doing here.

Generic code readers (e.g. I have a Sears one bought on ebay) can read the standard OBDII engine diagnostic codes, including the saved but no longer active ones that the blink codes may omit. They can also do code reset. But they may not get all the Honda proprietary codes or mislabel them.

You might have to pay for it, but a Honda dealer has the Honda proprietary plug-in diagnostic tool that can read all parameters as well as (hopefully) experienced mechanics to do complete diagnosis. Dealer quality varies.

Less expensive and perhaps free for a basic check, a trusted independent shop can also do computer diagnostic and inspection, but may not have the Honda proprietary unit. Honda protects the copyright on it, which makes the real ones expensive. II see "clones" advertized that run on a PC, but I don't know how good they are. And they aren't free either.

Al_NFR

Yeah it wont pass 8.4k at all even if i were to be going downhill, heres the video i promised, i just realized its not the best video but at about the 20 second mark of the video you see where my rpm stops rising, didnt want to hurt the engine so i didnt continue trying to pass the 8.4k mark and immediately dropped it into neutral https://m.youtube.com/watch?v=PrFRxeSyGbA

superchargedk20

I'm still going with my previous post. Somethings up with ur fuel delivery. Does the s2k ecu have a fuel cut if the motor runs to lean? If not something is up with ur fuel when it reaches those rpms

Kenshyn

Search for user Billman250 on here, link him to this thread. He's the go-to guy when it comes to these cars; he knows pretty much all there is to know about the S2000.

MBHs2k

Are you positive it's an ap1 ECU? An ap2 ECU would cut fuel at 8300

Billman250

First thing I would do is record one redline event with the scanner. See if the RPMs are actually reaching 9k, or the tach is skewing the reading.