crisskro

Update
Did not manage to find a s2k MAP sensor yet. Tried with another sensor from a different Honda, same shape and stuff, made no difference.

Took it to Honda, they couldn't find the cause for my problem. They had no way of testing the vacuum (go figure). They rewrote the ECU but the problem still remains. Running rich again, the O2 sensor I've replaced is acting up (high voltage) - I will check the service manual for the wiring, maybe a rat chewed some wire. When the O2 sensor was ok, the original problem was still present.
At least the engine runs very nice at idle.

S2Ks are rare in my country, hard to get a hold of someone who knows what they are doing

Billman250

Why the aftermarket fuel pump?

More I think about you might be running very rich....I'd look at the fuel trim at idle. That will tell you a great deal about whats going on.

crisskro

The aftermarket fuel pump was installed by the previous owner, along with a NOS system with unichip that destroyed the previous engine. After the previous engine was toast, the NOS and unichip were uninstalled, and a different engine was fitted. The ECU wires where the unichip was installed are ok now.

The fuel pump makes a wining noise as well, and that leads me to believe he has not fitted back the OEM fuel pump (because walbro pump usually sound like that).
I've asked the honda guys about fuel shortage, and they said the fuel pressure was ok - but I'm not betting my life on it.

What do you mean "fuel trim at idle"? Is this like hooking a AFR gauge and reading the AFR at idle?

Billman250

Not AFR. fuel trim. its read by the OBD2 system as a percentage. It will tell you what the ECU has been doing with the fuel over the course of your problem, adding it or subtracting it. You need an obd2 scanner that reads basic data to do so.

I would change the fuel pump back to stock also.

crisskro

I will do this after I fix the O2 sensor problem. Thanks a lot Billman.
Yes, I will also change the fuel pump back to OEM, (hopefully next month), along with that f-ing mishimoto 60 degree thermostat -> back to OEM, and the accessory belt while I'm at it.

Billman250

Didn't realize you had a 60 deg tstat. More fuel to the mix

crisskro

Yeah... just found out last week myself. I wondered why the hell is it taking so long until it starts heating up on the inside.

Edit: Thermostat was changed with oem.

crisskro

Weird that since I've took it to honda and they rewrote the ecu, the O2 sensor problem has gone. No check engine in a week.

One more thing I've found out just today. The previous owner has replaced the clutch, and I'm suspicious about the knock sensor. From what I've read, it can be damaged during clutch replacement. Could this be the root of all evil? I've noticed that the car is more drivable when using lower octane fuel (95 Europe) and worse when using 100 octane. Also when using 95 octane it does not buck so often.

Billman250

What do you mean re-wrote?

Is your CEL bulb working?

Broken Knock sensor will throw an immediate code. You could check to be sure it is the correct one and they didnt relace it with a cheap one. It should be green.

crisskro

They said that they rewrote the ECU, asked for my ignition keys, said something about relearning the keys. They said something about having to trick it into thinking they were replacing the ECU to get it done.

CEL bulb should be working, has not thrown a singe CEL since it has been to honda. Before taking is to honda, whenever I pulled the fuse to clear the check engine light, it usually came back on in 15 minutes of driving tops. O2 Bank 1 high voltage. (they have not taken out the CEL bulb, i was next to the car all of the time ) ).

Also no CELs related to knock sensor, but I do have someone in my city who has owned two S2000s and related to my problem, said it could be a vacuum leak or maybe the knock sensor. Problem is he's f-ing busy all of the time and can't get a hold of him in the last 2 weeks.