Oxygen Sensor turned red

[RV7LS1]

Questions:
1. What will turn an O2 sensor RED?
2. Why a new bouncing RPM indicator?

I have an LS1 in an RV7 kitbuild airplane. I haven't been able to find any mechanics that I trust who seem to know what they're talking about when it comes to BOTH airplanes and LS1 engines; so I decided to educate myself (just starting).

The engine was running rough and backfired on the R-side only. I replaced the R-side O2 sensor and it resolved. Immediately after this 10-minute repair, the RPM Indicator started bouncing by 700 RPMs but only when the enginge is between 1500-2300 RPMs. I replaced the L-side O2 sensor and the engine is even smoother, but still RPM needle bouncing:

[sunsetorangess]

Stuck injector or valve. Pull plugs and check to make sure there not fouled. Plugged cat may also be an issue
J

[RV7LS1]

Thanks a lot, I'll check on the plugs. The nice thing about the airplane is I don't need a cat.

[LS2Tuner]

Key ? here. . . . . . . . . !

You said it's in a plane. You are running 100 octane Aviation Fuel in it then you get at the air port right?

Even though MANY refer to that as a No Lead fuel it actually has a high content of lead.

Welcome to the site!

Can we get some pics?