Odd AFR

asc_up · Post by **asc_up** » Sun Feb 03, 2008 8:44 am

So my car was running great tonight.
I came home for a bit and then left.

As I was leaving I looked at my narrow band and it was reading extremely lean at idle and then when I full on gas it it says I'm running extremely rich.

Now, I know it's a narrow band so I can't have complete faith in it, but usually when I floor it I'm "stoich" (right between lean and rich).

So what would cause me to all of a sudden be running extremely rich at full boost and extremely lean at idle?

scuzzy · Post by **scuzzy** » Sun Feb 03, 2008 7:28 pm

the ECU has learnins about it.

It's not a worry to run lean at idle, since there's no load on the engine as long as it's not detting and your EGT's aren't through the roof, you'll be fine.

vrg3 · Post by **vrg3** » Sun Feb 03, 2008 10:03 pm

Sounds to me like something's wrong with your oxygen sensor or its wiring.

At idle the signal should be constantly changing, moving back and forth from lean to rich and back.

At full boost, it should be rich.

Also, a near-stoichiometric ratio on full boost can be dangerous to the engine, so I hope it was misreading before somehow.

Arctic Assassian · Post by **Arctic Assassian** » Sun Feb 03, 2008 10:06 pm

yeah, 14:1 is not good for turbo cars. I shoot for 11-12:1

asc_up · Post by **asc_up** » Sun Feb 03, 2008 10:58 pm

Ok. Thanks for the tips guys. I'm that worried about it running rich on boost. Lol.

But I started it up this morning to head to work and it would barely idle like I kept blipping the throttle because it sounded like it was about to die. Once it was warmed up everything was fine. It did this on my way back home from work, too.

vrg3 · Post by **vrg3** » Sun Feb 03, 2008 11:05 pm

Try disconnecting the oxygen sensor and resetting the ECU. If the only problem is/was that the sensor is bad, that should make the problem go away.

asc_up · Post by **asc_up** » Sun Feb 03, 2008 11:17 pm

So disconnect the O2 sensor harness and then unplug the battery from the car for 30 minutes or what ever to reset the ECU.
Reattach the battery and start the car WITHOUT the O2 sensor plugged in? Correct?

vrg3 · Post by **vrg3** » Mon Feb 04, 2008 3:20 am

Yes, precisely. You can drive without the sensor as long as you want. I even passed an emissions inspection without it.

asc_up · Post by **asc_up** » Mon Feb 04, 2008 4:37 am

Ok. So if I do this test and it shows that the O2 sensor is the problem, I should still replace it correct?

I'm just trying to understand the purpose of the sensor now if you say that you can drive around without it...

asc_up · Post by **asc_up** » Mon Feb 04, 2008 4:39 am

Also, as I was leaving to my friends house to go watch the Superbowl, the car was DEFINITELY pulling timing. Once it warmed up, everything was fine.

vrg3 · Post by **vrg3** » Mon Feb 04, 2008 4:41 am

Yeah, I'd replace it. You should get better fuel economy, and you won't trigger a CEL when cruising on the freeway.

asc_up · Post by **asc_up** » Mon Feb 04, 2008 4:46 am

Oh yeah that's a problem I was having, also. I was on my way up to Crystal Mt. and my CEL came on but disappeared after about a minute or two. Then it would come back 20 minutes later. It never came on during the drive back.

Could this also be related to the O2 sensor?

vrg3 · Post by **vrg3** » Mon Feb 04, 2008 4:54 am

Yup, sure could be.

asc_up · Post by **asc_up** » Mon Feb 04, 2008 4:55 am

Ok. Thanks for your help V!!

asc_up · Post by **asc_up** » Mon Feb 04, 2008 5:27 am

Well I checked my ECU codes, even though I don't have a CEL...yet.

It threw a 21 and a 32.

21 is for the water temp. sensor. I think that was just an old stored code because I had a problem with it before and now it's fixed.

The 32 is for the O2 sensor. Maybe it's from when I got a CEL on the highway?

I unplugged the O2 sensor and tried driving around without it, it was still pretty crappy. I've checked for any disconnected vacuum hoses but haven't found any.

So I'm still thinking the O2 sensor is the problem. Agreed?

I keep thinking that maybe I have a vacuum leak, but that would mean that I would have a rough idle ALL the time, right? I only get a rough idle when the car is warming up. Then it seems to run fine, but really rich...

Oh and as of the past two fuel tank fill ups, I'm getting about 18-20 MPG...

vrg3 · Post by **vrg3** » Mon Feb 04, 2008 6:10 am

You need to reset the ECU after disconnecting the oxygen sensor.

But, yes, agreed on all counts.

douglas vincent · Post by **douglas vincent** » Mon Feb 04, 2008 7:39 am

If you are running an O2 sensor through anything besides your
ecuu, do'tr belive it.

You NEED to have an external wideband reader to have good returns.

asc_up · Post by **asc_up** » Mon Feb 04, 2008 9:10 am

douglas vincent wrote:If you are running an O2 sensor through anything besides your
ecuu, do'tr belive it.

You NEED to have an external wideband reader to have good returns.

Haha ok. I was going to pick up an AEM wide band with my next paycheck.

P.S. Were you drinking or was that just a typo? hahaha

asc_up · Post by **asc_up** » Tue Feb 05, 2008 7:17 am

VIKASH I LOVE YOU (and I mean that in the least gay way possible)!!

I went to the Subie dealer today and got my O2 sensor. The car runs better than when I first got it! It's great. Hahaha.

Oh and the guy at the dealer said it was going to come out to $148.00 so I told him I'd like the one for the N/A Legacy and it was only $99.00. Hahaha apparently it costs them an extra $49.00 to shorten the wires on the same O2 sensor...

vrg3 · Post by **vrg3** » Tue Feb 05, 2008 8:10 am

Yeah, funny how that works. I'm glad the problem's solved.

Arctic Assassian · Post by **Arctic Assassian** » Tue Feb 05, 2008 9:01 am

wow. I did not know that they were the same O2. That is awesome to know.

asc_up · Post by **asc_up** » Tue Feb 05, 2008 11:10 am

Yeah they're exactly the same EXCEPT the wires on the turbo O2 sensor are shorter than the ones for NA cars. So somehow that makes it cost $50 more...??? Haha.

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Odd AFR

Odd AFR