I could really use some help here. My 2001 S2000 has a random misfire at idle. The first code is always 1399, but after a short time I'll have codes for a couple cylinders. Cylinder three (p0303) is consistently the first cylinder to code, but the rest follow until I pull 1399, 0300, 0301, 0302, 0303, 0304.

The misfire happens ONLY at idle, and I get a flashing CEL. Reving the car or pulling away from the light instantly makes the CEL go solid again. The car feels and drives just fine during the entire RPM range, goes into VTEC just fine, however it idles rough.

Here is what I've done so far:

- Replaced MAP with brand new OEM unit
- Switch Coil #3 and #2 (cylinder 2 is often the last to code a misfire) - No change, misfire still started in #3 and #2 is often the last to code
- Ultrasonically cleaned all 4 injectors - car felt slightly smoother, but no change in misfire idle issue.
- Replaced injectors
- Two valve adjustment's
- Cleaned ISV - car felt better, but no change in Misfire issue
- Replaced spark plugs
- Replaced PCV valve
- Replaced timing chain tensioner

I haven't ever mis-shifted or over-reved the car, so I don't expect the issue to be bent valves.

I've read tons of threads on here, most of the suggestions haven't worked or don't seem like my situation.

Anyone have any suggestions on what my next few steps should be, or have had the same issue with a fix?

Thanks so much for the help!

 

Have you done a compression test and cylinder leakage test? I'd do that next to see how the motor is. Are you modified? What mods.

 

I haven't done those tests yet. Not that this is justification not to, but the motor runs strong.

I have no mods aside from an 03 ECU. Stock from the intake to the exhaust.

 

well i havent had this car long enough for me to do spark plugs

but i gapped spark plugs for my friends evo mr on e85 and he put them in
and said it ran like shit and miss fired.

so i go open the hood and this spark plugs order is wrong and i just
its should be 1,2,3,4 he put something like 4.1.3.2 LOL

so i switched them back and it ran good as new and took out all the miss fire.

we thought it was something else like bigger as engine blown or spun barring.
but it was simple, you should try it!!!

 

I had the same symtoms. Changed brand of gas. fixed.

 

x2 on this


The car doesn't like ethanol, with oem ecu or even a tuned aem

for some reason, probably a local problem because we have a lot of shitty premiums in Canada

 

I've been through probably 25+ tanks of gas at multiple brands of gas stations. It's pretty safe to rule bad gas out.

 

I typically stick to the Shell by my house, but I have stopped at enough others to rule out bad gas at the station I typically go to.

No changes among tanks of gas, or gas stations.

 

does your car has carbon fiber hood?

 

No, The car is all stock. (aside from AP2V1's and 03 ECU)