ssmoke-u

I'm not new to the forum, but I did just purchase a '02 Z06. After only owning the car for a week i noticed the fuel economy is extremely poor. like 10 - 12 mpg poor. The car has an LS3 with Longtubes, high flow cats and stock Ti catback. Has ziptie mod for intake. I had a buddy hook his scanner up and it says O2 bank 2 is bad, but that is after the Cats. Would this be the culprit? I plan on replacing fuel pump and putting in new plugs as well as replacing the bad o2 sensor. Any other suggestions?

PS: when driving the car, at times i smell a bit of fuel. I have not gone to get a tune yet, but is high up on my list of things to do.

Any insight is greatly appreciated,

Thanks, Mark

ssmoke-u

No replies?? Jeez.

tblu92

4 sensors in all 2 are pre cat--2 are post cat
Identified as sensor 1 ( fronts)
and sensor 2 (rears )
Bank 1 is for the diver's side
Bank 2 is the passenger side
The rears (sensor 2 's) have no affect on engine fueling and are there only to report the condition of your cats
However the fronts ( sensor 1's) control all the P/T fueling
So if you have a failing front 02 yes it will be horribly rich --Even a lazy 02 will make it run richer---Plus LT headers always seem to make the eng run richer anyways even with good 02's because of the further aft placed 02 bungs---Be prepared to change them out every 2-3 years---
Bad rear 02's ( sensor 2) will simply throw a code--Most everyone has them "tuned out" with a full tune

Rx7Rob

Does the car have a stock LS3 tune in the computer??

ssmoke-u

Do not know what tune it has.

tblu92

You said your car is an 02 Z06 which came STOCK with an LS6 engine----But you said it has an LS3 engine--hence the confusion
An LS6 is a 5.7 liter engine with 405 stock HP
An LS3 engine is a 6.2 liter with 435 stock HP
The tunes are NOT interchangeable -and require different tuning
What engine do you have ? If you do have an LS3 in your 02 Z06 then someone has replaced the stock motor
If we know for sure we can help figure out what you need to do---But something IS wrong

umrjmac

When you are observing bad fuel economy is that what is shown on the in car display or are you doing the math based on the odometer and what the fuel pump says at the gas station?

Not all tuners are created equal...if someone used bad injector data and then fudged the rest of the tune then the computer's idea of how much fuel that it is using may be wrong even though the net amount of fuel shot into motor may be right.

The rear O2 sensors do not affect the air or fuel model that the computer uses to control fuel flow...they're basically part of the emissions validation system. If the cats are bad (and the sensor is still good) then it would be used to set a DTC, as tblu92 said.

ssmoke-u

I'm well aware of what the car came with and what I've got. It IS an LS3 and I have solved the problem. There was an evap line not connected under the hood. Hooked it back up and voila. Great economy, no more fumes and smoother idle.