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!

EDIT: Car is completely stock except for 03 ECU.

 

What kind of plugs did you use to do the replacement?

And is your car stock?

 

The recommended oem plugs. PFR7G-11S (stock number 7772)

The car is completely stock aside from 03 ECU. (Added to the original post)

 

Have you done the MAP sensore "whack" mod yet?

 

Well I tried that, didn't work, so I bought a brand new one along with that OEM zip-tie update that keeps the clip plugged in.

 

Did you double check the gap on the plugs or did you just install them. Sorry I need to ask to make sure that all the simple stuff is checked first before going off on a wild goose chase.

 

I gaped the spark plugs to the OEM spec before installing. (I've actually been through 2 set of new spark plugs) No worries, I appreciate the effort.

 

Did the problems start when you switched to an 03 ECU? If not how long did it run ok with the 03 ECU?

 

Have you done a leakdown test? Also, have you read up in the UTH section on S2KI? There's a wealth of info about this over there.

 

The problem did not start after switching to the ECU. I think 6 months or more went by before it started.

I haven't done a leakdown test yet. I've read the UTH section (and posted in it twice) as wrell as the sticky thread about misfires on S2ki.

 

This happened to me exactly as you describe. I had 8 bent valves(4 intake 4 exhaust), worn out exhaust valve guides and bad valve seals.

Good luck I spent about $3500 all said and done.

I have an 00 with under 50k miles

 

3500$... on what? lol damn.. woulda swapped a new motor in over that or rebuild for performance..

 

I built my motor for less and the rods cost 800 alone!

Find stock motors all day for 2 grand!

 

Well if you have done all else then yes I think a leakdown check is in order. Have you ever had a mechanical over rev? If so you could have caused some valve damage.

As for the inidvidual who spent 3500 that was problably taking it to a shop or stealership.

 

It's at the dealer today for a leakdown, test fuel pressure etc. Leakdown tester is 70+ and this was 115, so it was worth it even though I hate taking the car to others...

Will update when I hear back.

 

Alright, got the car back. It's a bent valve in Cylinder #3.

I may just swap so if you've got a swap in socal for a good price, let me know!

 

a bent valve is hardly a call for a new motor lol.. just replace the valves.

but if you do end up buying a replacement block lemme know if you wanna get rid of yours. i'll pick it up to build it

 

The motor has 166K on it, and I've been driving with a bent valve for a while. It may be a good opportunity/excuse to swap or rebuild.

PM me an offer for the block if you would like.

 

also be sure to check the spark plugs regularly as they tend to unscrew themselves. my S started throwing the same codes. misfire on all cylinders, turns out the plugs did exactly as i described. make sure theyre torqued to 18-22lbft.