Hey all. I have an 2001 Tibby.. no serious mods.. just aftermarket headers, CAI, and catback exhaust. I'm having a weird problem and it is just seeming to get worse. I'll start my car up, and if I DON'T let it warm up, it has SERIOUS problems accelerating. If I just start it up and take off, it doesn't want to accelerate hardly at all. I had it at the dealership and the only thing they said was they found out why my Check Engine light is on, and it's because I don't have my O2 Sensor hooked up. Could this also be the reason why I get poor acceleration? I'm not a huge motorhead or anything, so help a brother out a little bit, haha. Thanks. laugh.gif

 

in short

yes

 

hes right..

If your first 02 sensor is missing... your engine has no clue if your running rich or lean so your ECU places your car in "limp mode."
When cold, your engine has a start up fuel map which pretty much richens the A/F ratio. If your ECU has no clue how rich your running.. it will just add more fuel to an already rich condition.
Install it ASAP,... otherwise it will eventually kill your catalytic convertors... which will give you another CEL (2nd 02 sensor)

If your 2nd 02 sensor is missing/not connected,...
Your ECU will throw a CEL and put your car in limp mode. This is done to purposely cause you to replace your disfunctional car OR a non operating 02 sensor.

 

You never specified which o2 sensor is missing .. the first or second?
If it's the first, then YES.
If it's just the second one your missing, then you've got something else wrong.

 

theoretically could it be something other than the O2 sensor? (Not wanting to hijack my first post but, I have the same problem on my 99 tibby with no CEL... could still be my sensor but how does one know...).

 

Replace the sensor... that will tell you if thats the Only problem fing02.gif

 

^^^
correct me if I am wrong but I thought that the O2 sensor doesn't really kick in until after the car is warm because it has a filament that has to heat up to like 400 degrees or something like that. I always thought it was the MAF that controlled most of the A/F ratio while the engine is cold and waiting for O2 filament to heat up. Now don't get me wrong, having your O2 sensor disconnected is not a good idea anyway. I would definetly hook it up and see if that fixes it, that's the cheapest way to see.

MOD EDIT: quote removed
Please do not quote the post above yours.

 

Are you sure you have only one CEL for O2 sensor?

 

Well, I'm pretty sure it's the first one that's not hooked up. See I had those aftermarket headers installed and I could be wrong but I don't think there was a hookup in them for the O2 Sensor, so the place probably just didn't install it. It's weird though, because I had them put on like, a year ago.. and just fairly recently has it started giving me these problems.

 

you're right about the heated o2 sensor, you said it has to heat up to get a proper reading. correct me if im wrong, but the once it does heat up & if it gives a bad reading your long term fuel value (%) will be affected, which im pretty sure is what your car goes off of during an open loop (startup). and once the car warms up again it puts itself in limp mode to try and put the car in a normal stance.

hey, did the dealer tell you what needed to be done to correct the o2 sensor problem? i'd say whatever it takes to eliminate the o2 sensor problem would be a start, cause you need to fix that problem anyway. then you can start worring about the roughness of the car during start up. if you replace the sensor, you may have to drive the car a little to change the LT Fuel Trim back to normal.