my car is a 2007 civic si coupe. my mods are a kraftwerks supercharger kit (comes with its own intake and manifold), custom tune, full exhaust, stage 1 cams. i've had the supercharger and same tune for over a year and had no problems so i'm assuming it doesn't effect the issue. i did however switch to a 10mm smaller pulley without updating the tune about 3 months ago. lately i've noticed a lot of black buildup around my exhaust also more and more.

The real problem started a few days ago when i was driving to work. i heard the car sputter a bit but it would still drive normal-ish. then it started to lose power and die while i'm driving. i popped the clutch and it would come back on for a few minutes and lose power and die again while driving. putting it in neutral while driving also caused it to die right away (didn't hold an idle). eventually it wouldn't stay on longer than a few seconds. got it towed home.

now here is what it is doing. it will start just fine, no problems. it will idle semi-normal. and then after a second or two, it will rev up on its own to 1500rpm and then shut off itself. happens exactly the same every single time I try to start it. here is a short video of it happening. just replaced the fuel pump today with no luck. hope you guys have some good input!

https://www.youtube.com/watch?v=G31LLnc9Z8g&feature=youtu.be[/YOUTUBE]

 

Got around to swapping out the spark plugs and it started right up and stayed on no problem! old ones seemed to be fouled out

 

Sounds like you're running pretty rich if you have u burnt fuel building up and plugs fouling on you. Maybe swap back to the other pulley or get it tuned for the pulley on there.