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View Full Version : Checking precat o2 sensor



Poopie
11-22-2006, 10:43 AM
Is there a way to diagnose it? I don't get a check engine light, but I've been trying to tune my AFR using vag-com to log and adjusting my fuel pressure. From 35-psi on to 45 psi the afr doesn't change much when logging. I am running pc-16 getting 19-20 mpg city highway mixed This is the original o2 sensor for 66k miles. I think its about time to change it anyways right?

Neo1130
11-22-2006, 12:17 PM
How many miles you have? What AFR are you running?

Poopie
11-22-2006, 01:40 PM
66k miles and block 31 says I run a peak lambda of .9. It doesn't change much if I bump up or down my fuel pressure. the PC 16 file says I should run a new o2 sensor so I might just pick up at the dealership.

Does anyone know the conversion factor to go from lambda to the airfuel ratio? Mike says it should not go into the .9s and others say it shouldn't go into 1.0's

Poopie
11-23-2006, 08:10 AM
anyone?

SeanF
11-23-2006, 10:35 AM
14.7 if i recal correctly...

Neo1130
11-23-2006, 11:15 AM
Originally posted by SeanF
14.7 if i recal correctly...

I think that is if you have the wideband o2...

SeanF
11-23-2006, 06:10 PM
oh your right...

mike-2ptzero
11-23-2006, 06:30 PM
Originally posted by Poopie
66k miles and block 31 says I run a peak lambda of .9. It doesn't change much if I bump up or down my fuel pressure. the PC 16 file says I should run a new o2 sensor so I might just pick up at the dealership.

Does anyone know the conversion factor to go from lambda to the airfuel ratio? Mike says it should not go into the .9s and others say it shouldn't go into 1.0's


Well since you are a pre 01 car then the block 031 readings you are looking at are "voltage" not lambda, this is because you are running a 4 wire 02 sensor. The 01+ cars run a 5 wire which is a wide band and they read in lambda on block 031 and voltage on 031.

Voltage readings
.85 = about 12.5:1
.9 = richer
.8 = leaner

Lambda
.85 = 12.495:1(.85x14.7)
.9 = leaner
.8 = richer


BTW what is your 032 reading with the engine off?

Just make sure that the people that are giving you advice know about your model car not just all cars in general. Just like you wouldn't take your car to a honda shop to fix a problem on your Audi.

Poopie
11-23-2006, 06:59 PM
I'll go log block 32 later and report back. Thanks for the good info mike. I thought the closer I got to .9 the leaner it runs. I checked for boost leaks and I couldn't find any so we can check that off for why I'm running a bit rich.

01'A41.8T
11-23-2006, 09:27 PM
I thought PC-16 was known to run rich.

Poopie
11-24-2006, 06:22 AM
other way around. Known to run lean at redline but I am rich and not with money. har har har....=( sorry just got back from camping in front of best buy and walked away empty handed.