Y2K-Z28

I bought a 2000 Z28 from a guy on the cheap as he was needing cash. It had a horrible exhaust leak and the check engine was on. It ran OK and is a pretty nice car for cheap so I snagged it. Replaced the header gasket and it sounds fine now. When I bought it the upper O2 on passenger side was disconnected so I reconnected it. The car idles rough and almost dies and you can smell it's running rich. I know the rear O2's need to be deleted with a tune from reading other posts, but why is the car running better with top O2 unhooked. I'm an older Gen 1 engine but I know LS's are the future and I've had tons in daily drivers just wanted to try playing with one for a change so excuse my ignorance.

99Bluz28

iTrader: (35)

The exhaust leak likely would of caused the rear O2 to think the engine was running lean so all the extra fuel probably ruined the front O2 on the passenger side.

Can'taffordit

When I deleted the rear o2 on my engine and the front two went out it acted like it didn't want to idle and was running rich.

pdsq98gt

The O2 sensor is probably dead and reading low voltage. This makes the PCM think it's running lean and then starts to dump fuel into that bank causing a rich condition. By disconnecting it the bad data isn't seen by the PCM and it runs in open loop. No data is better than bad data. Try a new O2 sensor.

mpatton

Yup wat 98gt said. Its in open loop instead of having fuel trims.

Y2K-Z28

I'll change them then guys. Thanks so much for the info as i'm learning every day. Even though the cars been a lot of work i'm so glad I tokk the LS plunge as they are certainly the future. It was great to hook up the sensors after changing the intake and tranny and have the car fire right up instead of setting timing and adjusting idle mixture screws. It's making me want to do a transplant in the future. I'd love to make like 425-450 at the wheels without affecting drivability to much. I just love to surprise a Mustang at a stop light and it's tough to do that with a huge cam talking trash. HaHa!