Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Marks DTM Calib]

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!

[VXL V6]

Great work Mark.

I've heard 'cataclean' is good.

Thanks!  

[MikeDundee]

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

[Marks DTM Calib]

Great work Mark.

I've heard 'cataclean' is good.

Thanks!  

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.

[Marks DTM Calib]

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

These we can clean.....

[MikeDundee]

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

These we can clean.....

Some carb cleaner then?

[Marks DTM Calib]

No....a special cleaner in an ultrasonic bath.

[MikeDundee]

No....a special cleaner in an ultrasonic bath.

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

[Kevin Wood]

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

[Marks DTM Calib]

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.

[Marks DTM Calib]

No....a special cleaner in an ultrasonic bath.

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

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

[MikeDundee]

No....a special cleaner in an ultrasonic bath.

Really?,............ you winding me up .........I believe you Mark .........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?

[MikeDundee]

Or buy one of these?

http://www.bestultrasonic.com/

[Golfbuddy]

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

[Marks DTM Calib]

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

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

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.....