Bad O2 but no codes

[tweek814]

I recently picked up a 97 gsx, auto.. bone stock, sounds like it has a bad exhaust leak after the cat

repaired a bad boost leak, thought it was running good, but now im getting like 10mpg.. car produces a weird smell under boost, not burning oil.. thinking its fuel? but even driving lightly/hardly boosting im still not getting any better mileage. the car seems to be running ok, maybe a bit sluggish but its hard to tell because its been running this way since i bought it.

im not getting a CEL, could my o2 still be bad? i unplugged my o2 entirely and it still didnt throw a code

i dont have a garage and the ground is covered in snow, so i havent been able to check for fuel leaks or anything. but ive parked over fresh snow and after moving the car noticed no liquid had dripped. not even sure where to start, i guess ill get some new plugs and an o2? money is tight since i just blew it all on this car .

 

[JusMX141]

An o2 sensor will wear out gradually like a set of spark plugs. It's not until the sensor actually fails or shorts out that it will throw a code- especially on OBD1 vehicles.

A logger will give you a definite answer as you can monitor the o2 sensor's function....although if you're sure there are some miles on the sensor, just replace it.

 

[tweek814]

Not sure if its ever been replaced, car has high mileage tho. But when I unplugged the o2 it should have thrown a code right??

Gonna pick up some plugs and a new o2 after work and see how that goes.

 

[blkgst97]

Maybe the person before you had a CEL and took the bulb out to hide it while selling the car?

 

[tweek814]

I guess that's a possibility, maybe ill see if advanced can do a cel check while I'm there just in case.

 

[Ethand14]

A bad o2 wouldnt make you get that horrible gas mileage. Is it the rear o2 that you think is bad?

 

[my98gsx]

Replace the o2 sensors. Not only will a bad o2 sensor kill your gas mileage, but it will drop your performance. The smell under acceleration is the weird thing to me though. Does the car still have the catalitic converter? If your that starved for power and it is sluggish you can have a bad / clogged catilitic converter. This will have a sulfer smell to it while under a load. If you said the exhaust was rotted out and leaking it can mean your cat is also bad. If you are strapped for cash i would start with the front o2. This is what tells the computor how the car is running ( the rear only tells the ecu if the cat is working properly and does not control fuel ).

Before changing anything clear the ecu of codes with an obd2 scanner ( weither or not the car is throwing a CEL ) this will put the car back in open loop and make it check the sensors in order to get back into closed loop. Drive the car for 150 miles and hopefully a CEL will get thrown. It might help you with your problem.

 

[tweek814]

A bad o2 wouldnt make you get that horrible gas mileage. Is it the rear o2 that you think is bad?

i cant think of anything else.. i mean it could probably use a tune up to get the mpg's up a little but something is causing it to suck the fuel like a scythe.

Replace the o2 sensors. Not only will a bad o2 sensor kill your gas mileage, but it will drop your performance. The smell under acceleration is the weird thing to me though. Does the car still have the catalitic converter? If your that starved for power and it is sluggish you can have a bad / clogged catilitic converter. This will have a sulfer smell to it while under a load. If you said the exhaust was rotted out and leaking it can mean your cat is also bad. If you are strapped for cash i would start with the front o2. This is what tells the computor how the car is running ( the rear only tells the ecu if the cat is working properly and does not control fuel ).

Before changing anything clear the ecu of codes with an obd2 scanner ( weither or not the car is throwing a CEL ) this will put the car back in open loop and make it check the sensors in order to get back into closed loop. Drive the car for 150 miles and hopefully a CEL will get thrown. It might help you with your problem.

thanks for the response.. for starters, the car seems to be running good accept for cold starts. on a cold start, not letting it warm up, i really gotta step on it to get it to boost and pickup the rpms. after its warm tho it seems ok other than that smell under accel. performance wise im not sure because ive never rode in or drivin one of these cars.

the exhaust as far as i know is stock. with 154k on it. im planning on a turbo back exhaust soon tho, as well as a front mount, mainly to replace the IC piping..
o2 sensor was $98 at advance auto and bills are due so.... just got the plugs for now. the old plugs looked ok, a little dark but hard to tell how long they have been in there.

 

[joegamma1]

I got this one when i got my car, it was running funny and using a bit more gas than i thought it should, also with no cel(but my cel does definatly work, ). Good luck.

OBX OXYGEN O2 SENSOR 96-99 ECLIPSE GST GSX 4G63 FRONT : eBay Motors (item 160395672971 end time Jan-23-10 15:13:44 PST)