Omega Owners Forum

Chat Area => General Discussion Area => Topic started by: Marks DTM Calib on 03 January 2008, 08:45:29

Title: The 3.2/2.6 O2 sensor mystery.
Post by: Marks DTM Calib on 03 January 2008, 08:45:29
OK

Done some research and asked some people who work with Vx's on a daily basis (experts not mechanics!).

First, to clear things up......the value from the second 02 sensor should not change.....it should be constant as suspected.

Right, the setup on these units is that of a mixture regulation sensor followed by a small pre-cat, a cat check sensor and then the main cat.

One of the guys contacted has tried cleaning the 02 sensors on these and it made no major difference.

What we suspect is that the pre-cat is dropping in performance and this is being detected by the cat check sensor but, emissions are not affected at all thanks to the main cat being OK.

The suspicion is that the pre-cat is to small hence why its more prevalent on the 3.2 than the 2.6 (bigger engine more gas output).

This would also offer an explanation as to why using better fuels can help as these are likely to have a cleaning affect on the pre-cat.

The ideal fix would be for Vx to modify the engine software so its not nearly as sensitive to what is not a major problem.

Another possible is to run a good quality treatment through the fuel system with good cat cleaning properties to try and restore some of the pre-cat efficiency.....if such thing exists!
Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: VXL V6 on 03 January 2008, 08:58:47
Great work Mark.

I've heard 'cataclean' is good.

Thanks!  :y
Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: MikeDundee on 03 January 2008, 09:01:15
I have just replaced all my sensors, won't know whether that solves my problem until I get the EML reset. So have 4 very dirty sensors sitting in boxes in the kitchen ;D
Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: Marks DTM Calib on 03 January 2008, 09:04:43
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Great work Mark.

I've heard 'cataclean' is good.

Thanks!  :y

I also have heard good reports about cataclean....but if you use it remember that the Omega has a bloody big fuel tank so you need to take care on your dosing levels.
Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: Marks DTM Calib on 03 January 2008, 09:05:08
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I have just replaced all my sensors, won't know whether that solves my problem until I get the EML reset. So have 4 very dirty sensors sitting in boxes in the kitchen ;D


These we can clean.....
Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: MikeDundee on 03 January 2008, 09:10:48
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I have just replaced all my sensors, won't know whether that solves my problem until I get the EML reset. So have 4 very dirty sensors sitting in boxes in the kitchen ;D


These we can clean.....

Some carb cleaner then?
Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: Marks DTM Calib on 03 January 2008, 09:12:48
No....a special cleaner in an ultrasonic bath.
Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: MikeDundee on 03 January 2008, 09:16:51
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No....a special cleaner in an ultrasonic bath.

Really?,............ you winding me up ;D.........I beleive you Mark ;D.........never knew about ultrasonic baths, very interesting :-/
Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: Kevin Wood on 03 January 2008, 09:18:45
Thanks for the information. Interesting... I guess the pre-cats are the devices in the elbow of the exhaust where it turns rearwards below the manifold? Always wondered what was in them, and why the post cat sensors weren't behind what looked like the cats :-/

Given that MOT emissions are still fine without them, and that their only purpose appears to be to drive  the emissions light, the bodger in me wonders if the signal from the post cat sensors can be spoofed to keep the ECU happy? After all, I'll replace the cats when the emissions are no longer MOT compliant, not when a light on the dash tells me, thanks.

Kevin
Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: Marks DTM Calib on 03 January 2008, 09:30:00
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Thanks for the information. Interesting... I guess the pre-cats are the devices in the elbow of the exhaust where it turns rearwards below the manifold? Always wondered what was in them, and why the post cat sensors weren't behind what looked like the cats :-/

Given that MOT emissions are still fine without them, and that their only purpose appears to be to drive  the emissions light, the bodger in me wonders if the signal from the post cat sensors can be spoofed to keep the ECU happy? After all, I'll replace the cats when the emissions are no longer MOT compliant, not when a light on the dash tells me, thanks.

Kevin

Yes, the pre-cats are the part mounted in the elbow with the heat shield around it.

I am sure the use of a few resistors or resistor-zener setup would do a nice job of keeping the ECU quiet.
Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: Marks DTM Calib on 03 January 2008, 09:32:16
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No....a special cleaner in an ultrasonic bath.

Really?,............ you winding me up ;D.........I believe you Mark ;D.........never knew about ultrasonic baths, very interesting :-/


Ow yes....they are often used for cleaning, excellent for jewelery, cds, watch straps etc.
Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: MikeDundee on 03 January 2008, 09:38:53
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Quote
Quote
No....a special cleaner in an ultrasonic bath.

Really?,............ you winding me up ;D.........I believe you Mark ;D.........never knew about ultrasonic baths, very interesting :-/


Ow yes....they are often used for cleaning, excellent for jewelery, cds, watch straps etc.

Obviously need to send off to a specialist then for cleaning?
Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: MikeDundee on 03 January 2008, 09:39:55
Or buy one of these?

http://www.bestultrasonic.com/
Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: Golfbuddy on 03 January 2008, 09:49:57
As most of you know, I don't know a lot about engines and how they work. I was interested though to read the article in the following link regarding engine cleaners and treatments.

I make no comments as to it's validity, I will leave that to cleverer men than I, but it does make interesting reading.

LINK (http://www.fuelsaving.info/cleaners.htm)
Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: Marks DTM Calib on 03 January 2008, 09:58:28
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As most of you know, I don't know a lot about engines and how they work. I was interested though to read the article in the following link regarding engine cleaners and treatments.

I make no comments as to it's validity, I will leave that to cleverer men than I, but it does make interesting reading.

LINK (http://www.fuelsaving.info/cleaners.htm)


Your right.....he knows nothing (but doesn't claim to!)

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Anything strong enough to dissolve years of deposits in just a few seconds may well also attack sensitive components such as manifold pressure sensors, which are not generally designed or tested to be resistant to such cleaning products

No chance of a cleaner getting anywhere near a MAP sensor.....its a fuel additive and you dont get fuel back up the inlet. And even then, MAP sensors are on a stub so no air flow.

We are talking about a one off dose here to try to resolve a problem on higher mileage cars as an alternative to spending 1000 quid on cats.....

Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: Kevin Wood on 03 January 2008, 10:16:46
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Your right.....he knows nothing (but doesn't claim to!)

He He. If in doubt, give it a good spanking! A proud graduate of the Italian school of car care!

Kevin
Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: SP_3.2 on 03 January 2008, 10:58:21
Hi all just had a look at the website for Cataclean and seems like a good product. I have found a stockes near my work and was thinking of runing up a trying some at lunch

What do you guys think of it it,s £16.50 Having the 02 prob as its seem most of use are with the 3.2,s.

Thanks.   :y
Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: Kevin Wood on 03 January 2008, 11:34:10
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What do you guys think of it

Got to be worth a try, I guess. Like most lotions and potions for use as additives they make some impressive claims. Whether it's snake oil or not remains to be seen. At least you have a problem at the moment, so you will have an idea whether it's done anything or not.

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I am sure the use of a few resistors or resistor-zener setup would do a nice job of keeping the ECU quiet.

I wonder if the ECU is clever enough to look for activity on the post-cat sensor when the cat is cold, and verify that it disappears when the cat gets hot, or if it is enough just to never have any activity...?

Kevin
Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: SP_3.2 on 03 January 2008, 15:43:12
Just to get this right when you talk about pre and post 02 sensors is that going from under the car looking towards the engine so the 1st set are the pre and the ones after the bend are the post or is it the other way around. I belive that one set stay at one reading and the other set swich from lean to rich would that be right.

Thanks

Steve.   :y  
Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: Marks DTM Calib on 03 January 2008, 16:09:46
Quote
Just to get this right when you talk about pre and post 02 sensors is that going from under the car looking towards the engine so the 1st set are the pre and the ones after the bend are the post or is it the other way around. I belive that one set stay at one reading and the other set swich from lean to rich would that be right.

Thanks

Steve.   :y  

The one closest to the engine (above the bend) is they mixture control sensor.....the one between the bend and cat is the monitor sensor
Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: SP_3.2 on 03 January 2008, 16:50:53
Thank you .   :y
Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: MikeDundee on 03 January 2008, 17:51:46
Here are some pics of the Lambda/02 sensors pre & post;

(http://i85.photobucket.com/albums/k65/mickdundee_01/Lambda02pre-sensor.jpg)

(http://i85.photobucket.com/albums/k65/mickdundee_01/Lambdapresensor2.jpg)

(http://i85.photobucket.com/albums/k65/mickdundee_01/lambda-02postsensors.jpg)

(http://i85.photobucket.com/albums/k65/mickdundee_01/postLambda022.jpg)



Title: Re: The 3.2/2.6 O2 sensor mystery.
Post by: SP_3.2 on 04 January 2008, 09:38:25
Thank you MD that a great help  :y