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[mkaminski100]

Many folks in Poland and in UK ask me a question about catalytic converter faults in 2.6 and 3.2 engines. I know that this topic was here many times but I just can’t find it now. I don’t have this engine but I would like to help them.  They get 420 & 430 errors and even if deleted it keeps coming again after a time. Sometimes it’s a week sometimes it a month.
Emission test are ok, there are no leaks in exhaust system. O2 sensors are working fine.
What do you suggest?
Petrol? Many of them are saying that they’ve tried all sorts of petrol without success
Knackered O2 sensor? Is there any way to clean it? What are a proper O2 sensors readings in these engines?
Both sensors are in front of main catalytic converter  so it shouldn’t be a CC fault. Is the first box a catalytic converter? What does it do?
Havy anybody tried “CataClean”? Is it worth £15?

Thanks for your help.

[Marks DTM Calib]

Loads of posts on this one.

The small box mentioned is a pre-cat and once the efficiency of this drops off then you get a fault raised yet MOT figures will still be fine.

The solution is to move the post cat sensor to after the main cat.....and I notice recently this has been tried and proven now.

[mkaminski100]

Yes, there's always plenty of topics when you dont need them, but when needed you cant find them (or being lazy...)
Thanks.
Am I understanding correctly? Second sensor needs to be moved behind the main Catalytic Converter?
This is how I understand it:

Am I right?

[Marks DTM Calib]

Exactly right.

The wires are long enough to allow it to be done without any modification and weld on bosses and blanking plugs are readily available

[Kevin Wood]

If running LPG doesn't cure this I will be doing the same, I think.

Interestingly, fuel quality does seem to do something. If my light is going to come on (and it's on more then it's off these days) it'll be about 5 miles following warmup on the first cold start after refuelling, regular as clockwork. It'll then stay on for 1 1/2 tanks of petrol or so.

Maybe the time taken for the fuel trim to respond is slow enough to push an already borderline cat over the edge?

Kevin

[Maurizio Ceresoli]

I resume that topic, while i'll have the same issues soon.

As i assume the 2 sensors are sending a signal to the ECU, isn't it possible to fit dummy sensors sending always the right signal for a warm engine?

I bet all of us here are car-keen pesons and while the car is cold all of us go nice and slow under 2500rpms, so this should'nt make any engine problem.

[TheBoy]

I resume that topic, while i'll have the same issues soon.

As i assume the 2 sensors are sending a signal to the ECU, isn't it possible to fit dummy sensors sending always the right signal for a warm engine?

I bet all of us here are car-keen pesons and while the car is cold all of us go nice and slow under 2500rpms, so this should'nt make any engine problem.

Move the sensors as suggested

[Maurizio Ceresoli]

Well, i WILL have this problem as i'll remove the cats... i'm working on a toy car.
 

[feeutfo]

Well, i WILL have this problem as i'll remove the cats... i'm working on a toy car.
 

Aaaaaaah...Falken in your sig...  .  <runs screaming from room with inner ear infection> 

[Kevin Wood]

As i assume the 2 sensors are sending a signal to the ECU, isn't it possible to fit dummy sensors sending always the right signal for a warm engine?

Not really. The ECU goes through a test cycle of swinging the mixture over a range of values once the correct engine conditions are met. It monitors pre- and post cat lambda sensors during this process to determine the behaviour of the cat. I think it would be difficult to spoof this behaviour, although some say a delay between the two sensors is all that is required and that shrouding the post cat sensor achieves this. I did set out to try this but the lambda sensor didn't fit the shrouds I bought. 

[Maurizio Ceresoli]

As i assume the 2 sensors are sending a signal to the ECU, isn't it possible to fit dummy sensors sending always the right signal for a warm engine?

Not really. The ECU goes through a test cycle of swinging the mixture over a range of values once the correct engine conditions are met. It monitors pre- and post cat lambda sensors during this process to determine the behaviour of the cat. I think it would be difficult to spoof this behaviour, although some say a delay between the two sensors is all that is required and that shrouding the post cat sensor achieves this. I did set out to try this but the lambda sensor didn't fit the shrouds I bought. 

I'll try using a lambda emulator they use on LPG equipped cars, keep you informed.