Idle Issues

[philipviana]

My 2016 rc390 was having strange idle issues. It would run at 2500rpm, then surge to 4000 for a few moments, then go back to 2500. Over and over. At higher RPMs the variation seemed to diminish. I remembered that I may have not properly reconnected the air hose at the back of the air box (underneath the seat / toolkit area), so I removed everything from that area and reinstalled the hose to be secure. Now the idle is stable at 2500. (Separate question: How does the air box get any air when all of this is relatively sealed up inside the rear seat?)

But now there is a new problem: any time i raise and then close the throttle, the idle drops below 2500, close to the point where the engine would stall. I'm wondering what's going on with the air on this bike.

Throttle is properly adjusted with ample slack so that turning the bars fully does not cause any throttle surging.

The bottom of my OEM exhaust, where the metal bracket connects to the bottom fairing, has a hole in it (the bracket rusted and came loose). Could this be causing some kind of air/pressure issue? Or is the exhaust not having any impact, and I should be looking elsewhere, like raising the idle speed?

 

[Biker]

I have exactly the same problem. As it showed a faulty lambda code (low voltage) I replaced the lambda sensor but now the check light is coming on intermittently (at idle) saying there a fault with the sensor again (1 long, 7 short flashes). On riding it goes off but am getting issue with the rpms dropping at low speeds or sometimes surging.

Btw I also replaced the iacv. Also did a full service myself including cleaning the injector. All else is as it should be including no leaks afaik. Further the issue started prior to the service.

I also have the piggyback Powertronic ECU.

The issue is driving me nuts and any help much appreciated!!

 

[1JZSupra]

On the duke there is a snorkel that goes to the air box and it pulls air from the back of the bike. I have an intake pipe setup since as I got tired of replacing air boxes due to cracking. With that being said I have an intake air scoop I made up. I'm in the process of designing intake air scoop V2 from ABS plastic. This scoops up air and directs it up to the filter.