[s-cars] RE: Emissions Test Failure

[Kaklikian, Gary]

Thanks for the response, Bill.

The O2 sensor was replaced recently and appears to be working fine. There is no hesitation other than just off-idle and gas mileage is good. The thermostat was also replaced recently and the car normally runs at the second (bold) hash mark on the gauge.
Also recently replaced were the plugs/boot, air filter, and fuel filter.

 The car only failed in HC and only at idle in the basic test. CO and CO2 were a bit high, but within the limits and consistent at idle and 2500rpm. It also failed a more elaborate test on a dyno, in which they plot the emissions across time and speed. It shows the HC spike off-idle, coincidental with high CO and CO2 readings.  This leads me to believe it is a richness off-idle and not a lean misfire.

I'm replaced the throttle switch ($$) today since it's original, but I don't think this is the cure. I'm also pulling the injectors to replace the seals. I may send them in for servicing to RC Eng or GBR as well since I really don't know what else to do at this point. There were no codes stored in the ECU.

Any other suggestions are greatly appreciated.

Gary
-----Original Message-----
From: William Noland [mailto:wenoland at pacbell.net]
Sent: Wednesday, May 22, 2002 6:39 AM
To: Kaklikian, Gary
Cc: s-car-list at audifans.com
Subject: Re: Emissions Test Failure


Gary -
Have you checked the O2 Sensor?  I'd agree that you're running rich.
 The ECU will default to its last mixture setting before the sensor goes
out, if it, or the wiring, has gone bad. One other possibility would be
a bad thermostat.  If you're water temp gauge isn't consistently getting
to the first bold hash mark, your thermostat may be toast.  If the motor
isn't warming up properly, it could be running on the rich side.  I was
experiencing a rotten egg (rich idle) smell, which was drastically
reduced, after replacing the thermostat.  Temp gauge shows the motor
finally warming up properly now.

Bill Noland

>
>My '92 S4 failed  the emissions test, in particular the hydrocarbons at idl=
>e were very high. All other readings (CO,CO2) were normal at idle and at 25=
>00rpm. The car has had a stumble off idle recently, so I suspect it may be =
>running rich at idle. I checked the throttle switch per the instructions on=
> S. Mockry's site, looked for vacuum leaks, and pulled the ECU codes, all t=
>o no avail.
>