I have been driving my S2000 and have noticed it seems down on power. Then every now and again it'll feel like I have 100+ more horsepower.

Not sure what the cause is, could it be fuel filter, injectors, fuel pump?

 

Bump, this is so frustrating. The dealer had no idea, suggested it was the fuel filter.

 

Not sure where you're located, OP but this car is HIGHLY sensitive to ambient temperatures. For me and my MY07, when the temp passes 70 degrees, the car can feel like a dog, especially if I've been driving it for a while. When it gets down into the 40's and 50's, it's like a monster lol. Anyway, this time of year when temps are in the 40's at night and climb to near or above 70 during the day, you're going to notice power spikes.

Unless there is truly something wrong but I'd think you'd get some more indicators if that were so.

Oh also, just to add, you can check routine things like if the injectors are clean and if you haven't taken it for a valve adjustment yet, that may be something you want to do regardless of mileage.

 

When this car sits for a while, it gets warmer, and the timing seems to get knocked down a lot.

One thing to try is changing gas. You may not be getting 91+

 

I had the valves done about a year ago. I should check the injectors and plugs I think.

 

I've been using Shell V-power here in Los Angeles. Any fuel suggestions?

 

Try cleaning the MAFS and the air channel.

 

It was the shitty valve adjustment Alhambra Honda did. Its fixed and FAST again.

 

The Honda dealership is the worst place to take your car. The horror stories ive read on here about dealer " repair " are god awful...

Shell 93 is the best gas IMO... its all i use unless forced to use something else.

 

That is not always true . There are some very good Honda dealers that due excellent work ! I find Exxon/mobile to be about the best pump gas to be found .