pastfast125

I was talking to my uncle about me gettin my o2 sensors hooked back up. His opinion was that getting those hooked up will affect my air/fuel ratio and cause me to run really lean. His reasoning was that the o2 sensors are designed to set the a/f ratio in a way that benefits gas mileage and smog the best, thus leaning it out. Is this true that I will be running lean then? He said it normally wouldn't be a problem, but with the big cam it affects the motor more. Can anybody clarify this for me? Sorry if that was kinda vague sounding, just tryin to learn here.

Also, a tune will take care of any a/f ratio problems correct?

greenstreak9205

no, if you car is fuel injected ur gonna need to hook those back up. they dont lean the engine out, they keep the engine running correctly. yea it helps with the mileage and stuff, but if you dont "plug" them back in ur car is gonna run like crap or definately not to its full potential. it can actually cause the engine to wear out considerably faster by washing down the cylinders with all that extra fuel.

pastfast125

They haven't been hooked up since christmas

Previous owner never had em on and i never got around to buyin some and gettin em hooked up, but I lost my license for 2 months so they're one of my priorities now.

And what I was trying to say was, with the oxygen sensors in, on a stock setup, it's gonna run slightly lean for gas mileage and emissions right? So that with the combination of aftermarket cam would make it run leaner? Atleast that's what my uncle was saying, I'm just trying to learn if this would happen and why or why not.

greenstreak9205

I would make it one of my top priorities. but thats just me

Joel5.0

The O2s are the feedback sensors for the EEC-IV, the confirmation devices for any trimming (rich or lean) the system does to the A/F. In your case, you're running under a "failure mode" or FMEM strategy once the system determines there is no feedback from the O2s, and using a set of parameters based on "estimations" from the temperature and load readings/calculations the system does....which is not very effective.

Connecting the O2s (which I suggest you replace, they should be contaminated by now) will allow the system to set A/F to the correct setting.....yes emissions is key (that's why EFI was created), but performance and driveability also suffers from too rich of a condition. Not using them will not cause premature engine wear or a "wash down" condition unless, another failure is present in the system + you may be allowing it to run rich, but forcing the system to take spark advance out (typical of the FMEM strategy)......which is not good for performance anyway.

Suggest to set it right, and allow the computer to do its stuff......otherwise, a carburetor setup would work better.

luckythirteen13

joel is correct. the o2s dont lean the motor out. they just tell the computer what the motor is doing. if you motor is running rich now, yes, hooking the o2's will lean it out. if your running lean now, hooking up the o2's will richen it. with the o2's help, the computer will shoot for 14.7afr which is fine when just crusing