Wisconsin S2k

we should try to find out if it applies to only 02-03 or if it's all AP1. good info.

S2k007

I'm having the same problem but its not at start up. It usually occurs when i coast to a stop at a red light. The revs seem to drop to low and it just dies. I live in Irvine, CA so its rarely that cold here. Do you guys suppose its the same problem?

Wisconsin S2k

it's very likely. follow the steps I gave above. this happens during driving, coming to a stop as you stated, just as much as during startup.

xviper

Although not exactly the same, it is "similar" and very common. Again, don't help it. Just be prepared to hit the starter button if it dies. If it just stumbles, odd as it may seem, this is a good thing. It will help the ECU learn to cope better. Your situation is also related to atmospheric conditions of air temp, air pressure, humidity, engine temp, intake temp, air density and oxygen content at specific parameters related to road speed, gear, deceleration. The ECU has a momentary inability to keep the idle up. As you decel to a stop, the injectors have cycled off. It knows that you are slowing down. However, all the sensor signals it's getting confuses it and it "forgets" to hold idle up when it gets below the prescribed rpm. It tries to "catch it" but sometimes, it's too late. That's when it stumbles and, if your car is either slightly lacking in maintenance (air filter, plugs, etc) or if you try to help it by altering the throttle position, it has a much harder time dealing with it. It can also be aggravated with the use of the air conditioner. The added load of the compressor if it cycles on at that moment, can also make it hard for the idle system to cope.
Some have asked, "Why does this car do it so much when others don't?" I believe it's because our cars have very high output engines (given the displacement) and is tuned (read: ECU programming) to run reliably at the "edge". This sort of thing is not entirely isolated to S2000's. My old ZR-1 Vette did this also, as did my Viper on certain days. It was in the programming. They could program out the stumble/stall, but then, this took away from other areas of engine performance.
I'm content with Honda's programming. The engine is a fine piece of machinery but it has its little quirks. The quirk is not so much that it sometimes stumbles and stalls. The quirk is that it needs us to sometimes leave it alone so that it has a chance to learn.

S2k007

Ah, thanks guys. I usually hold the gas slightly so it doesnt stall when it starts doing it a lot, I'll just let it "learn" from now on. Its very sparatic though and I did the whack map sensor trick, seems to be fine for now.

SenderGreen

Speaking of ECU's and learning, I'm under the impression that at least on the MY 02-03's you can't VTEC for about 2-3 days after a reset (depending on how/when car is driven/enable criteria). I noticed when I reset my ECU on an 03 that the kick of VTEC transition was gone. I was also watching my continuous IM/Smog monitors slowly set themselves. I can't remember if it was on the second or third day when the last remaining IM monitor set itself, but as soon as it did the kick of VTEC transition returned. I know how much stock people put in the butt-dyno, however I was watching IM monitors as well and think it more than coinsidence. I mention this here because a reference was made to another thread (removed) where someone who was running without the no. 25 backup fuse was giving advice about idle and saying his car runs great, so I wonder does that mean great minus VTEC? Also I have seen Billman250 (who IS an authority) tell people before to reset the ECU and VTEC is good to go. This is why I wonder if this applies to 00-01 S2000's. Anyone have any info, thoughts? No flames please I'm sharing an observation.

xviper

First, I'm not convinced that the person in question (running without the BACK UP fuse) was entirely from this planet, but that's another story.
Mine is an '00 and I can tell you without any shadow of a doubt, that without a BACK UP fuse, the car barely idles and runs poorly when trying to move off from a stop. Once the revs were up and kept up, the ran fairly normal. Upon slowing down, the idle would drop very low and sometimes stalls, just like it was having a brain fart like so many have reported when occasionally, they come to a red light or stop sign and get that studdering idle momentarily. The main difference being that without the fuse, the idle never picks up on its own.
I have also reset the ECU both on my car and on a 2002 model and I can also tell you that both cars were able to VTEC once the engine got to "3 bars", with no discernable difference in VTEC function.

SenderGreen

Interesting, only today I saw a thread on immobilizer stuff where one guy agrees with me. https://www.s2ki.com/forums/index.php?showtopic=60618 .
Also I can remember one guy who said he couldn't VTEC, it turned out he had just had something done at the dealer where his battery was disconnected. However if you and Billman250 both disagree with me then it is most unlikely.

EDIT: Don't get me wrong, I was talking engine warm, and able to pull above 7k, just wasn't feeling VTEC cam. I know, I know butt-dyno. The butt-dyno is probably what you're going by too, no? I could swear as soon as the IM monitors finished setting it was back. I guess that could be percieved in my mind because I was watching them.

xviper

Yes and no. I generally can also hear the VTEC transition besides the butt dyno feeling the "kick" as it goes "on the cam".
I'm not trying to insult you in any way but when you test for VTEC, you do know that it's best done with WOT and in the lower gears (preferably 1st), right? Anything less than WOT and you can get a tremendously variable VTEC transition that may or may not be felt. Also, low oil level will cause some difficulties.
(Just making sure we're on the same page.)

SenderGreen

I think I remember something about VTEC oil pressure test is something like 1st gear above 6500 (don't remember) for x seconds. Does it have to be WOT? Can't remember. I am not insulted, I appreciate your knowledge. I admit I was not flogging it when I noticed this phenomena. I guess if I really have to know I could hook up an LED to the VTEC test lead, reset the ECU, hook up the scanner and go for it. Do you know if there is a better way to monitor VTEC transition other than T-clip to the wire? Like the test lead for the Tach under the hood. Maybe we could get someone who already has the LED to try.

EDIT: Maybe someone at a dealer? They have to able to hook something up to check VTEC engagement.

EDIT: oil level should have been good. I must not have getting on it hard enough I guess.

EDIT: Don't you have an oil pressure gauge? Would that be enough to tell? I'm not asking you to reset your ECU, just would that be enought to tell beyond doubt if someone else is willing?