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[SteveMJ]

My engine light came on a couple of months ago and the fault was one of the pre-cats (advice taken from on this forum) and reading the code.  I've been fillng up with 'super' fuel - again as the advice from this forum is regarding the benefit of extra detergents in it.

I've put quite a few tankfuls through now and it seems that every time I fill up the EML comes on after a day or so and then goes off  about 1/2 of the way through the tankful.

This is not what I'd expect; I expected that once the cleaning was done and the EML light extinguished then it would remain so.

Not sure if this is relavent but the car feels smoother since the use of the alternative fuel.  I still only get about 22mpg on my 18 mile daily commute of mixed side roads and dual carriageway/motorway.  I'm sure it was nearer 28mpg last summer (maybe just warmer weather)?

Thanks for the input.

[Entwood]

Have you done the "pedal trick" to confirm th fault codes are 0420 and/or 0430  

It's possible that the codes are something else ....

Mine seems to keep the codes off for long periods , but I often drive it hard on longer journeys, a good 40 mile tow seems to get everything nice and warm .... the LPG might help of course as it burns cleaner ..

[belldarr]

Mine has been on almost constantly for the past 4 months - so annoying!

Is replacement of the pre-cat sensors the only option??

Darren

[feeutfo]

Mine has been on almost constantly for the past 4 months - so annoying!

Is replacement of the pre-cat sensors the only option??

Darren

If you mean moving the sensors behind the main cats? Then yes, apart from replacement of the cat section, bugger that. The sensors themselves are not the issue  unless you have a sensor specific code, as i understand it. Do pedal trick and post results to be sure.

Some members have reported good results by using
Super unleaded etc. But this probably means the cat is borderline? Maybe?

Just waiting for mine to come on.... Going to happen one day .

[SteveMJ]

Pedal trick  - that's a good idea (I feel I should have thought of that - but didn't); got code 0420 this evening - so that is the pre cat isn't it?

The EML light went out yesterday (~1/3 tank gone) BTW.

[Entwood]

0420, 0430 are the two pre-cat codes ... one for each sensor...

[feeutfo]

Pedal trick  - that's a good idea (I feel I should have thought of that - but didn't); got code 0420 this evening - so that is the pre cat isn't it?

The EML light went out yesterday (~1/3 tank gone) BTW.

Yes thats pre cat efficiency code, 0430 being the sensor in the cat on other bank of cylinders, dont know which is which.
Only cure is to move 2nd 02 sensor behind the main cat, that way the gasses are given a good scrub before the 2nd sensor sees them. Seem to remember reading about buying 2 sump plugs, same thread as sensor, and weld the boss into the exhaust then screw the plug into the old sensor hole. Albatross and SP 3.2 have done this on their cars. If your exhaust is on the way out, maybe get a hand made stainless system and get them to move the sensors at the same time.
 

[SteveMJ]

Could I just rewire the front section lambda cable to be in parallel with the rear rear one?  This would be much easier than all that drilling, welding, tapping etc?

Cheers

[Kevin Wood]

Mine has been on almost constantly for the past 4 months - so annoying!

Is replacement of the pre-cat sensors the only option??

Darren

If you mean moving the sensors behind the main cats? Then yes, apart from replacement of the cat section, bugger that. The sensors themselves are not the issue  unless you have a sensor specific code, as i understand it. Do pedal trick and post results to be sure.

Some members have reported good results by using
Super unleaded etc. But this probably means the cat is borderline? Maybe?

Just waiting for mine to come on.... Going to happen one day .

That reminds me. I've got a datalog to look at.

Kevin

[Kevin Wood]

Could I just rewire the front section lambda cable to be in parallel with the rear rear one?  This would be much easier than all that drilling, welding, tapping etc?

Cheers

No. You're relocating it the other way - after the main cat, so it's seeing "clean" exhaust gases.

Kevin

[V6 Gix]

So does using super unleaded actually make that much of a difference?

[Kevin Wood]

So does using super unleaded actually make that much of a difference?

Who knows? The higher octane rating will make no difference. Marketing hype suggests that there are more additives in super, so who knows? I suspect a lot of it is down to better consistency (always filling up with the same brand at the same garage) meaning the block learn values are not chasing up and down all the time. When my EML wasn't always on it did seem prone to light in the first few miles after a fill-up.

Kevin

[Marks DTM Calib]

Nothing to hard about drilling the exhaust and welding a few bosses in

[Proz]

I have one sensor before and one after my main cat , didnt make any difference to mine  

[SteveMJ]

I'll try to make one answer to the comments  from a number of your answers above:

a) for me (I'm an electronics engineer) to drill and tap is a mission - not easy at all  

b) If the exhaust is drilled and tapped after the 2nd cat then this will be next to the exisiting 2nd lambda sensor (if I understand correctly).  So why not just connect the wires from the front lambda sensor in a parallel with the existing one already there behind the second cat?

c) to stop the the EML beign illuminated I want the lambda sensor to be seeing a 'clean' exhaust - don't I?


Thanks for you time