Hey guys,
I just got my first S2000 about 3 weeks ago!! I flew to Iowa to get the car and drove back to Utah.. it took me about 18 hours
It's 2000 AP1 NFR 65k. It has few problems which is check engine light on for P0420 also the fuel pump makes noticeable whining noise at Idle ( the previous owner said that the noise is from exhaust but it turns out that the fuel pump was making the noise )
The previous owner's mechanic said that the upstream o2 sensor needs to be replaced and I replaced the o2 sensor but the light came back on. From what I've been reading in the forum, P0420 can caused by faulty o2 sensors, damaged cat and etc(engine misfire, low fuel pressure or high fuel pressure)
The car runs smooth except sometimes the idle is rough. when I press gas slightly and let it go then the rpm goes down to 300~500 rpm but comes back in a second.
I made a list to check and replace and hoping you guys can point me in the right direction!

1) check or replace fuel pump ( Since the car has only 65k, it's stock fuel pump and I don't know if it's normal for stock fuel pump to make noticeable whining noise at idle. I think It gets louder when the car's been driven more than one hour. Should I replace it or change the filter and clean the fuel pump?)
2) check or replace spark plugs
3) check or replace downstream o2 sensor ( I already replaced upstream one but didn't replace downstream o2 sensor )
4) check or replace cat (I'm not sure if it's clogged or damaged but since it has 65k probably the cat is not clogged)

I'm not a mechanic but from my understanding P0420 can be caused by low fuel pressure. do you guys think the fuel pump is causing the code or is it just my imagination?
also sorry for my English, this is my second language and I'm still learning it

 

 

I heard about the spacer and yes it will solve the check engine light but what about the rpm drops and fuel pump noise? is it normal?

 

The fuel pump noise does not seem normal. The only time I hear my fuel pump is when I switch on the ignition before starting and even then if the heater fan is running it's barely audible. I'd isolate the noise "for sure" before diving into the pump. My DBW car has no fuel return so the pump run duty may be different from the fuel return-type systems.

The fuel pump assembly includes the filter and is located inside the fuel tank. I helped (OK, mainly watched) a fuel pump swap and it was accessed thru the trunk. A new pump and filter were fit into the assembly on the bench and the assembly returned to the tank.

-- Chuck