96–00 Civic, manual, D16Y7 with Y8 manual intake. Chasing an intermittent idle surge and rhythmic hesitation around ~1500rpm at steady throttle (feels like fuel cut/2-step). Car will sometimes run perfect, then act up again. Consistently throws P0505 (IAC system malfunction) when the issue is present (solid CEL only). Unplugging injectors one at a time smooths idle and reduces hesitation; unplugging IAC causes immediate sputter. Found raw fuel smell in the FPR vacuum line; pulling the vac line causes instant surge. Reseating/blowing out the FPR vac hose made the car run perfectly for ~1 hour (idle + driving), but symptoms returned after unplugging/replugging IAC. ECU reset + relearn helps temporarily but doesn’t last. No overheating, no milkshake oil, no white smoke. Leaning toward fuel pressure / failing FPR causing ECU/IAC compensation limits → P0505. Replacing FPR and vac hose next — looking for confirmation or anything else to verify once fuel pressure is corrected.

 

https://www.tiktok.com/t/ZTrWdxQvK/
this is a video with my exact issue. although this is a teggy and mines a civic

 

bump

 

nother bump