x99ChevyCamarox

I have pacesetter longtubes, ory and magnaflow catback on my car and i believe i was told by the guy i bought the car from that it does not have rear o2 sensors from when he put the new longtubes on. do i need rear o2 sensors if i put dual cutouts right after my collectors? and are there front o2 sensors and rear or what?

Fixxer99TA

iTrader: (5)

You will still always need the front two O2 sensors, the PCM takes readings from them and calculates air/fuel by it. If you put cutouts right after your collectors on your LTs, you will still need the O2s for the readings.

Front two are most important, they are used for the readings. The rear two are just to see if the cat/cats is/are working, so you dont need those

transamws6_97

iTrader: (5)

yeah what he said the fronts take readings to read your air to fuel ratio but the rears are pointless in the actual operation of the car. Most likely if you aren't setting off a ses light and there is no rear o2's he either has a sims or he got them tuned out

-PEPE-

iTrader: (10)

Great advice above, I'd also recommend just running 02 Simms for the after-cat 02 sensors, I think you can still get them from Summit, supposedly a couple years back they were going to outlaw them, but I don't know for sure. They aren't expensive and just prevent codes from being thrown by simulating a multi-level voltage reading using whatever resistor the sims use.

I ran it on mine (when I had PEPE) and it worked just fine.

Fixxer99TA

iTrader: (5)

There was a thread floating around here awhile back that had directions and a parts list to make your own for cheap. So if they are outlawed, then you can do a search and then hit up radio shack or something and do them for cheap!

nickp650ss

How bad is it to have O2 sensors that dont work anymore still in. I'm talking only about the front 2. Also what brand sensors are a good buy on a head/cam car?

ThreeHonks

iTrader: (10)

The car adjusts the A/F ratio with help from the front O2 sensors, so if these are bad the car will have decreased performance and may run rough

FiredUpZ28

Denso makes pretty good O2 sensors. Tell you what, its more unbelievable, than bad, that you have 2 bad o2 sensors. Have you checked the wiring to see if its faulty? Also , make sure you don't ever splice o2 sensors. The wiring actually allows air to pass through it to get to the sensor for its readings.

TDavanzo

iTrader: (3)

If you're putting cut-outs after the collectors then your o2 sensors are in front of that. If the car has an off road y pipe then whether or not the guy tuned them out they're gone.

You should be just fine running your cut-outs there.

petechapter50

iTrader: (1)

if you have a 95 or older you dont have a second set of 02's

Formula350

iTrader: (3)

Think of the O2 sensors as being related to a tuned carb. If they're working right and your car is in check then it's going to be in tune. If your O2s are bad then it's like having an out of whack carb. If you have NO O2s, then well I can't think of a fair analogy lol You better be some sort of tuning GOD who can smell at the air, lick his finger, and figure out what settings need to be changed on the fly. Even then, not sure if that'll do it haha