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View Full Version : Double Question. O2 Sensor necessary, Wheel Bearing removal



jhoney
09-01-2011, 03:10 PM
Im getting mixed reviews. I need to change my B2S2 as per code. I personally think it's murdering my gas mileage. but it may be psychosomatic. Some people on different forums are saying that if it is past CAT then it's not really a big issue to worry about. then another guy tells me it is affecting my gas mileage as it is telling my "MGD?" how much to open. ??? Im stumped.

Secondly. how hard is it to remove and replace L Front wheel bearing. its making a clicking sound and i just lifted it to spin and sure enough its the bearing.

colony7
09-01-2011, 03:51 PM
the rear 02 sensors do not affect your MPG at all. the only compare the readings from the first 02 sensor to determine how well your catalytic converter is working. wheel bearings suck dick on these cars. you have to remove the entire steering knuckle and have a shop press out the old one and press in the new one, and only use OEM or you'll regret it in about 2 months

jhoney
09-01-2011, 05:13 PM
right on. i heard about needing a shop to press it but what's a steering knuckle?

colony7
09-01-2011, 05:15 PM
the steering knuckle is the whole big ass metal arm that all your suspension parts connect to

walky_talky20
09-01-2011, 06:45 PM
Contrary to popular belief, the rear O2 sensor (Sensor 2), is indeed used for air/fuel mixture correction on most B5's. From the B5 Bentley:

Oxygen sensor control behind catalytic converter is superior to oxygen sensor control before catalytic converter and is responsible for final control correction.

It is the primary sensor and can override the signal from the oxygen sensor control before the catalytic converter.

So we shouldn't be so quick to dismiss the rear O2 sensor from causing mixture issues. As I recall, it gained some notoriety for causing "dumb rich" issues with SpeedTuning software a while back.

*However, this rear O2 sensor control applies only to 1.8T, 2.7T, and 30V 2.8 engines. Mention of rear O2 sensor mixture control is specifically omitted in the B5 documentation for the 12V 2.8, so I would assume that in this case it does not apply. I am going on the assumption that we are talking about '97 2.8 car in the OP's signature.

jhoney
09-01-2011, 08:50 PM
so you're saying the 12v 2.8 is an exception to the rule and in fact the o2 sensor might not play any role in air/fuel mixture. interesting. the bentley manual specifically excludes it??

walky_talky20
09-02-2011, 05:21 AM
so you're saying the 12v 2.8 is an exception to the rule and in fact the o2 sensor might not play any role in air/fuel mixture. interesting. the bentley manual specifically excludes it??

The bentley manual describes (in quite some detail) the strategy the ECU uses for mixture adjustment based on the rear (Secondary, Behind Cat) O2 sensor. However, this information is only included for 1.8T (specifically ATW and AWM), 2.7T, and 30V 2.8. There is mention (but no specifics) listed for the AEB 1.8T, and there is no mention at all of rear O2 sensor mixture control for the 12V 2.8, as far as I have found. Of course front (Primary, Before Cat) O2 sensor mixture control is described for every engine.

anmagro
06-13-2012, 09:29 AM
Contrary to popular belief, the rear O2 sensor (Sensor 2), is indeed used for air/fuel mixture correction on most B5's. From the B5 Bentley:

Oxygen sensor control behind catalytic converter is superior to oxygen sensor control before catalytic converter and is responsible for final control correction.

It is the primary sensor and can override the signal from the oxygen sensor control before the catalytic converter.

So we shouldn't be so quick to dismiss the rear O2 sensor from causing mixture issues. As I recall, it gained some notoriety for causing "dumb rich" issues with SpeedTuning software a while back.

*However, this rear O2 sensor control applies only to 1.8T, 2.7T, and 30V 2.8 engines. Mention of rear O2 sensor mixture control is specifically omitted in the B5 documentation for the 12V 2.8, so I would assume that in this case it does not apply. I am going on the assumption that we are talking about '97 2.8 car in the OP's signature.

I'm not sure if I'm bringing this thread back from the dead but I have a problem. What are you talking about when you speak about speedtunings rich code problems? I have a speed tuning tune and am experiencing rich on both banks and am currently doing research