boman993

Freaking out a bit....

Hey guys, so the inevitable happened, on the way home today the CEL came
on and the car started to run a bit strange. Here's what's happening:

1. The car seems to be burning really rich, I can smell the cat and even saw a bit of smoke when I stopped at traffic lights.
2. Has an erratic idle when coming to a full stop with the clutch depressed ~ The RPMs drop to 250ish and then back up to 750-800s and down again, and then evens out.
3. Seems to have lost it's pep a bit as well, though this might be in my head, I basically limped home once the light came on.

When I finally got home, I scanned the CEL and it's showing the P0140 code. I've done a search and it points to my O2 sensor bank one sensor 2.
Would this error make the car dump a lot of fuel? idle erratically? Is this as simple as replacing the O2 sensor? Or should I be more worried??


This is nuts, because when I drove TO work this morning, the car purred like a kitten..

Anyway, any insight is appreciated!

boman993

60+ views and nobody experienced this before?

trophy

Just replace the sensor and you should be fine... 96 and onward relied heavily on the o2 sensors for emissions (how much fuel etc). If they have never been replaced it may be time just to replace all 4 and be done with it, the other post cat sensor will fail eventually too...

User 122821

Caution driving the car if it's overly rich as it will kill the catalytic converter which are becoming rare and expensive to replace.

911Dave

I'm surprised that one bad O2 sensor could cause such rough running!

PNogC2S

+1 to both of the earlier comments.
Running too rich for an extende period of time (or too lean for that matter) can do damage and "Yes" a bad O2 sensor can wreak havoc with how an OBDII equiped car runs because it's computer is trying to compensate for what the sensor is telling it.
Get that sensor replaced right away... Don't drive around as is!

boman993

Thanks for the advice guys!! Now where to buy the sensors from? And should i get OEM? Agreed that
I will just bite the bullet and get all 4..I believe they're all original still...

Car is now parked until I solve the problem.

Jackstand Louie

Is it possible to have a faulty O2 sensor but no CEL?

My 99-996 was idling less than smooth so I scanned it. No pending or stored trouble codes. When I looked at the O2 sensor readouts Bank/Sens 1-1, 1-2, and 2-1 all have varying voltage readings in 0.1 to 0.7v range and fluctuate slightly. Bank/Sens 2-2 range is 0.02 (suspect) to 0.4v and seems to camp on 0.4.
Could the heater be okay but the sensor readout faulty? No misses under driving and heavy throttle. Idles a little bumpy. Plugs/coils have not been changed to my knowledge.

Stats:
62,000 mi
Tubi exhaust
EVO air intake (clean, no visible leaks)
Not a daily driver...no stop and go.