I’ve got a weird issue I’ve had since I got the car and I can’t fully pin it down. From a stop (light or stop sign), when I accelerate after stopping, whenever the RPM’s hit about 1000, the car hesitates/surges slightly before continuing to accelerate. Very rarely it has actually stalled before because of this.
I once did an idle relearn about a year ago (I usually reset ECU by disconnecting battery), and right after that, the hesitation triggered a flashing CEL and showed a cylinder 4 misfire code. That code never came back after that and I currently have no codes or lights (no ghost codes either).
The issue happens every day when warm. Cold start/when engine isn’t at operating temp, it doesn’t happen at all. In park, it will occasionally do it too. Whenever i rev the car (lets say to 5k or so) when the RPM’s are dropping, it literally does a little dance and wiggles around 1000 RPM. Also, when starting the car after it was just on (when warm), it sounds like the car struggles to start because it’s hitting that 1000 rpm spot.
So far I’ve ruled out spark plugs, intake/MAF/vacuum leaks, throttle body, and basic maintenance items.
Recently I also started noticing a deeper rumble/uneven sound between 1000–2000 RPM that sounds like a mild misfire, which makes me think it may be getting worse.
My current suspicion is ignition coil (possibly cylinder 4 since that was the only cylinder that ever flagged before), but I’m open to ideas before I start throwing parts at it.