[s-cars] Emissions fun

[tedebearp at yahoo.com]

I just replaced the O2 sensor and air filter a few weeks ago.  Plugs were fine although sooty.  Changed oil.  It didn't help.  The numbers were actually a bit worse.

Running lean could result in a lean misfire.  Here are the numbers:
Idle (779 rpm):
CO2 12.3%
O2 2.5%
HC 315 ppm
CO 1.06%

2642 rpm:
CO2 13.7%
O2 0.7%
HC 76 ppm
CO 0.74%

I checked the FPR directly with the vacuum pump and it held vacuum fine.

AC works fine whether the car is moving or not, and whether in fresh air or recirculate mode.  Sometimes recirculate works, sometimes not, but the AC always works.

The recirculate issue may not be related to the smog test failure.  There is an exhaust leak and I can smell exhaust coming through the vents when the car is stopped, which means it's probably coming from under the hood.  All of the nuts seem to be tight, but maybe the gaskets need to be replaced.  It occurred to me that an exhaust leak might cause the O2 sensor to incorrectly indicate a lean condition, resulting in the engine running rich.

What's a good way to find exhaust leaks?



Sent from my iPad

On May 22, 2012, at 6:16 AM, "JAM" <jscarstuff at charter.net> wrote:

> Not to be captain obvious but when was the last time you replaced the O2
> sensor?  Generally, it will go bad and the ECU doesn't pick it up and  not
> throw any codes.  My gut tells me that if you have a vacuum leak, you'd run
> lean because you have extra air getting in beyond the MAF but that's just a
> hunch.
> Good luck!
> Jason
> Boone, NC
> '95 S6
> '83 urq
> '90 CQ
> '01 A4 1.8tq
> 
> 
> 
> My '92 S4 isn't passing the idle portion of the smog test due to high HC.
> It does fine in other areas.  I've noticed the engine idles a little roughly
> and the exhaust smells rich.  No codes.  I also noticed the AC won't stay in
> recirculate mode reliably.  Sometimes it switches back to fresh air as soon
> as I push the recirculate button.  I'm looking for a vacuum leak.  I already
> replaced all of the vacuum hoses for the ECU and FPR a few years ago.  I
> disconnected the hose from the intake manifold and tested it with a vacuum
> pump.  No leaks there.  My next area of testing is the vacuum hose right
> below that one, which goes to the plenum and all the HVAC solenoids.
> Unfortunately my vacuum pump chose to crap out at that point, so testing
> will have to wait until I get a new one.  In the meantime, those vacuum
> hoses look original, so I'm going to replace them.  Anybody know the size?
> 
> Also, where is the vacuum solenoid for the recirculate flap?  Is there a
> good vacuum hose diagram in the Bentley manual?  I didn't see it.  I'd like
> to find a picture that shows me where the hoses and solenoids are in the
> car.  The hose from the intake manifold attaches to a plastic tee.  One hose
> from the tee goes into the plenum where it ends in what appears to be a
> check valve in a large canister.  The other hose from the tee is a fabric
> covered hose that attaches to a thin plastic line that runs down and
> disappears into a grommet in the firewall.  Anybody know what this one is
> for? 
> 
> Sent from my iPad
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