Flashing CEL during prolonged VTEC use (3rd gear+)
 

I am having a nightmare weekend with my S2000! I signed up for a track day at Auto Club Speedway here in Socal for today (Saturday) and tomorrow. Earlier this morning on my first session out, 2 laps in, the car began to flash a CEL and went into a sorta limp/weak mode when I was in VTEC in 3rd gear @ around 8k RPM. The "limp mode" was the engine not increasing RPM or speed while I held my foot down on wide open throttle. The CEL became solid as I got off the track and into the paddock and checked the CEL codes and found P1259 (VTEC malfunction) and P1399 (unknown cylinder misfire).

I did some webMD s2ki diagnosing while in the paddock and we decided to try disconnecting all the VTEC solenoid/switch wiring, cleaning off the connectors, and replugging them. I cleared the codes and went for a test drive and the car behaved normally until I kept it in VTEC at 3rd gear for a while. It began limping again and stuttering at 8k RPM and the CEL blinked.

We (my dad and I) decided to call it a day early in an attempt to diagnose/fix the problem properly at home so that I may be able to salvage the track day tomorrow. On the way home I wanted to show my dad the issue (I know... I should probably not be doing this) and again it only reared its head while in VTEC for prolonged time in 3rd gear, upper RPMs. Again the CEL flashed during the limp mode and this time it stayed solid.

When we got back home I checked the codes and we had 4 stored codes (P0300, P0301, P0302, P0303) and 1 pending code (P1399). At this point I referred to the Honda manual and looked up P1399. Based on the fact that it had previously shown a P1259 I went to that page and followed the step by step instructions... basically see if the car engages VTEC in first gear for a couple seconds then try it multiple times. If so check wiring and connections, your VTEC unit is fine... Well my car can do that no problem, the problem only rears itself with prolonged VTEC use in high gear (which is why it only appeared during my track day, I don't normally drive this fast on the street!).

So we decided to investigate the VTEC solenoid issue a little further. We took the VTEC solenoid off and inspected/cleaned the filter (it was clean) and cleaned all the parts before reoiling them and putting them back on the engine. I checked the oil level and it was topped off (I topped it last night for my track day prep). We also checked the ECM harness plugs and unplugged and replugged all of them. Lastly we took off the spark plug cover, removed the coil packs, and took out the spark plugs. We had just replaced the spark plugs two weekends ago with OEM plugs that were all correctly gapped and correctly torqued to 24 lb-ft.

The one thing that my dad noticed was that there seemed to be a little bit more black soot (?) around the first couple threads than he would have expected. The center and tip were fine. We cleaned off the plug threads, replaced and retorqued them to 24, and I changed the swapped all the coil packs around. I reset the ECM via the fuse method and then started the car, let it idle for a bit, then took it for a very spirited test drive.

The same issue occurred, again, and only after very long wide open throttle in third gear at around 8k RPM. Blinking CEL and went away and I pulled over and scanned it on the spot, pending P1399 (cylinder misfire).

At this point I'm a bit sad and frustrated as we had spent a lot of time over the past month prepping the car and I lose two track days ($410 combined...). I'm planning on following the misfire thread (https://www.s2ki.com/forums/s2000-un...thread-659930/) but in the meantime I figure I would ask on the forums because the issue seemed very specific.

Here are some notes/more information:
-my engine/intake/exhaust/ECM is completely stock
-two weekends ago we replaced my AP1 valve retainers and keepers with AP2 valve retainers and keepers (we also replaced the valve stem seals)
-I did the valve adjustment myself and it was my first time. I did not feel the previous valve clearances before we removed the assembly, I guess I should have done that
-we replaced the valve cover gasket and spark plug stem seal gaskets and the spark plugs at this time
-I drove 30 miles on the car and then the car wouldn't start the next day. it ended up being a bad battery, we took it in for testing and it was "wayyyyyyyyyy bad" according to autozone. we put in a fresh battery and the car started without any issues afterwards.
-I did 150miles on the car during the week after this... no oil leaks, no issues (but I wasn't driving like a madman, just hitting VTEC here and there but not too long)
-last weekend we did an oil change and added a mishimoto sandwich plate for an oil temp and oil pressure sensor (AEM)
-we also added two gauges for the sensors
-we added the modifry oem ap1 ECT module
-I drove the car for another week and did 150 miles on it, again hitting VTEC on occasion but never as much use as it seems is necessary to solicit the issue. No leaks, no issues otherwise.


Questions/my thoughts:
-maybe I adjusted the valves too tightly? or too loosely? I used bent feeler gauges and erred on the side of tighter.... could this be why the spark plug threads seem overly black so quickly?
-I tested VTEC in gears 1-4 to make sure I could clearly feel and hear the VTEC engage at 6k and it definitely engages correctly and disengages as well... this leads me to believe it isn't a VTEC solenoid issue but the original P1259 concerns me...
-I don't think it's the coil packs or the spark plugs because the car is fine 99% of the time, only during extreme conditions does it seem to misfire. The gunk around the threads though is concerning seeing as the plugs are only 2 weeks old but maybe that's normal for an s2000? Sorry I should have taken a picture...
-I did a track day 4 weekends ago at buttonwillow (during which time the car was fine, had no issues with prolonged wide open throttle, high RPMs, etc)... this allows me to at least isolate this issue to the last month! it leads me to believe it may be something to do with the maintenance we performed, maybe the stem seals or the valve adjustment.


Lastly... should I just cave in and have a local s2k expert (like Evasive or Rockstar Garage) look at it? Normally my dad and I handle all maintenance and fixes ourselves but I'm worried that every time I test to see if our new "fixes" actually fix the issue I may be damaging something more expensive... I would prefer we fix it ourselves (and learn in the process) but again I want honest recommendations.

Thanks and sorry for the wall of text

Have you observed the oil pressure when the problem occurs?

I don't think I stared at the gauge directly while the issue when wide open on the throttle but as soon as I backed off the throttle a little bit I looked at oil temp and pressure and coolant temps and they all seemed within acceptable ranges.

Whip the mishimoto plate of and retest is my thought,easy to do also ?

I guess I will get around to trying that after I do a couple more things first (valve adjustment, compression test)

I used the Honda manual and DIYGuys' youtube video as a reference:
I tried to set them closer to the tighter end of the range...
Intake: I aimed for the .008 to have low drag and for the .010 feeler to not fit... I did not check if the .007 should move freely - might have had too much drag for the .008 if I can't fit a .010?
Exhaust: same idea for this side, i wanted .010 to have low drag and for the .012 to not fit. again i didn't check if the .009 should move freely

this was my first time doing a valve adjustment and I used the valve adjustment tool.

I will pull off the valve cover and check clearances in a couple hours (at work now) and adjust as needed.

Do you think it is okay for me to test if the car is "fixed" after that? I'm worried about continuously fixing-and-testing... should i get a test pipe before continuing to test my fixes? i'm worried that the misfires could be harming my cat