Fvall

Hello guys bought the s2000 about a month ago, everything was going fine at first but now a days im getting an idle that is a bit shaky and a random misfire when at idle. Im like 99% sure that when driving there is no issue.

Issue is more noticeable when starting the car after it has been sitting for a couple of hours, i will be getting a cel that flashes for like 10sec because of the random misfires and then it will stay steady to on with the engine jumping up and down 50 rpm at random.

I first suspected the pcv but when shaking it i can clearly here it rattle. I ran the engine with the hole completly plugged but its the same idle with rpms being maybe a little lower. When running it completly free engine runs great, but at a 2.5k rpm idle. Hose seems to be uncracked and free of blockage.

Tried knocking the maf sensor around but no change, when i unplug it car stalls right away, so a asume this means its working fine ?

Next up im thinking about spraying soapy water on every vaccum line since it feels like a vaccum issue with it being only at idle.

Let me know what you guys think, im starting to run out of ideas.

engifineer

What is a full list of codes being set? And if a vac leak is causing it, it should also be setting some sort of stuck lean code or similar as well. A vac leak allows unmetered air into the system and thus can show up as the ECU seeing a constant lean condition. They can also cause rough idle, but typically will not cause a major misfire issue unless bad enough to set other codes as well.

When misfires occur, it is common to see the random misfire code first and then it will start setting specific cylinder misfire codes. If you see misfires on only some cylinders, then an easy first check is to swap coil packs between good and bad cylinders and see if the issue follows the coil packs. It is not uncommon for multiple coilpacks to fail close together on this car. Just ran into 3 failing on mine recently and just replaced all of them. But it could be many other items, coils are just super easy to swap around to see if that changes anything.

How do the plugs look?

But priority 1 is seeing a full list of the CELs being set

Fvall

The codes im getting are in orderthat i read them on the reader : misfire on cylinder 1, 2, 3, 4 and then the misfire at random cylinderand the one for the cat that i dont have.

I also started getting louder and louder backfires, but i recently changed exhaust so it probably has to do with the exhaust being different and its break in period.

P0420 6 - 7 --------------- Catalyst System Efficiency Below ThresholdP0301 7 - 1 P1399 ____ Cylinder 1 Misfire DetectedP0302 7 - 2 P1399 ____ Cylinder 2 Misfire DetectedP0303 7 - 3 P1399 ____ Cylinder 3 Misfire DetectedP0304 7 - 4 P1399 ____ Cylinder 4 Misfire Detected
P030# and/or P1399 __ Random Misfire
I removed all plugs and they looked fine, 2 and 4 were slightly whiter than 1 and 3, but from what i have seen on the internet they should still be good.
i also reinstalled them by changing the ones from 1 and 3 to 2 and 4 but there has been no change at all.

also since i havent mentionned it yet the car is a 2000 and as an intake and exhaust, no cat. Otherwise should be just about stock

RolanTHUNDER

Did you check your plugs for excessive gap or even the wrong type of plug? Is/was there any oil on your coil packs? Are your coil pack connectors making full contact with the coils themselves? Sometimes if your coil pack connector clips break, you might not get a good seal.

Fvall

I did check the gaps an they were within specs. I also dont think the issue is with plugs since the issue is on all four cylinders.

Coils packs looked fine to me but i can try to remove and clean the them i guess. But then again having 4 packs with bad connection would be surprising

Slowcrash_101

Sounds like a fueling issue.

engifineer

I would try to test fuel pressure to see what it looks like. The rub there is Honda has no typical port to do so.. and they spec an adaptor (that of course they sell for about $80 IIRC) to connect a standard fuel pressure gauge in place of the fuel pressure damper, which is annoying as hell. And if you do that you need to get new sealing washers for putting the damper back on to make sure they seal well. Some drill and tap the rail and just install a gauge themselves right on the rail. I really dont want to go that route since I do not trust a gauge to never fail and start spewing fuel why I am on track! But it is an option some take.

I have not dug in to see if there is a way to fab up your own adaptor vs buying the Honda one though. I read a couple of places it is an odd size and fitment so maybe not.

Fvall

I will try to find a way to mesure the fuel pressure, but if the pressure was bad wouldnt the engine be starving when going full throttle?

Right now the misfire issue only seems to be at idle

and i have tried different gas station in case the fuel i got was bad

engifineer

Yeah typically the fuel pressure would be more of an issue under load and not just at idle. My failing coils actually showed up more apparent under idle and it would smooth out under higher rpm at first, but the power loss was noticeable. The misfires were just more apparent at idle at first.

If you know someone close by with an s2k that is willing you could try just swapping coil packs with them to see if that is it. 00-05 coils will work in an AP1, 06+ needs to be 06+ coils on the drive by wire models. And if it is coilpacks that bit of info that the 04/05 work on the AP1 is pretty key as they are literally half the price of 00-03 coil packs. Even from Honda.

The coil packs dont fail from being dirty, they fail from the internal insulation on the coils themselves failing over time. And it is actually not uncommon to have multiple fail at the same time like mine (3 of 4 failed... car was running perfect, then while idling started misfiring on a cylinder, very quickly progressing to more). It is not intuitive to have multiple fail at once but it can happen and has to many of us, especially on an AP1.

Injectors could be the cause as well. Again you would think it would show up more under load but you could pull them and have them checked/cleaned.

windhund116

What did you do to avoid getting a CEL for no CAT?

Thanks!