I'd follow-up with leak-down test. Esp on #1 and 3.

Good luck!

 

The Honda S2000: "very fast, sleek, sexy, precise, rigid chassis, pure sports car, full of racy character AND VERY RELIABLE"

OP should just get the compression figures checked.

 

I have had this issue with mine, I was using Shell V-Power when it happened, I switched to a different premium fuel from Tesco (in the UK) and in the past few months I have not had a single issue, I wouldn't say the car runs any better or worse but it is no longer throwing me that P0303 code.

 

Really?? I'm using Shell 95 V Power all the time. Is it possible that fuel can cause a misfire/stumble issue?

 

Yep, I had previously had injectors refurbished and compression checks done, they were all fine but I still got the code, fuel change and no problems since!

 

Geez what are the chances?! I currently have a slight stumble issue that occurs randomly but only at idle. Sometimes pulling up to a light and it doesn't even happen but other times it does. Ran injector cleaner twice several months ago with a few months in between them. Did valve clearance myself but that didn't make a difference to this issue. Fuel filter was replaced at the dealer about 27000kms ago in 2014 so can't be that. The stumble never exhibits itself immediately when the car starts. It happens about 30 seconds or so after the engine is started...doesn't happen anywhere else in the power band far as I can tell, car pulls so strong.

Might as well give other fuels a try then unless an injector or two need a thorough sonic cleaning?

 

If fuel was causing misfires, it was bad fuel (or a coincidence).

 

That's true

 

I was thinking bad fuel but it wasn't just one Shell fuel station I filled up at and it was over the course of many months, I think the Momentum fuel has a slightly higher octane rating or it could have had different additives in it that worked better.

 

That is very interesting. Are your injectors quite audible during idle? Just curious.