What in the world would cause this?

[brianw21]

What in the world could cause this?

98 Vette with LG long tubes. As soon as it goes into closed loop the LTFT go to max in opposite directions. Repeatably.

With the headers the rear sensors were moved to the front. This scan was on a stock tune. With the rear sensors turned off it does the same thing.

Exhaust leak? Bad Sensor?

[svede1212]

i'm confused. you are running the rear sensors as the fronts? if so they won't work like that

[ajt86]

if your using the rear 02 sensors in the front they are looking for a pretty steady reading since the emissions should be burned up, there should be a steady amount of o2 in the exhaust at that point, if you have them running in the front, they will be seeing the pre-burnt exhaust and will set a catylist efficiency code

if you have the fronts hookup up in the back not hooked up- it will really mess with your fueling

i guess we need more info on what sensor is where and are there any cats in the picture......

[Hool97]

Do you have air injection hooked up? This will send air into the header before the O2. If one side is blocked and the other is faulty or gets all the air then the O2 will read free air on one side and likely rich on the other as the computer tries to richen up the AFR/ This is one guess.

[brianw21]

LG has you use the rear sensors in the front wiring harness. The rears are (were) turned off by disabling all sensor 2 codes.

[Chris@HPTuners]

your O2's are plugged into the wrong sides. swap them over and all will be well