2000 W Reg Bongo v6 failing emissions mot test

[pikey]

Our Bongo has failed its MOT on emissions. Reading was 0.4 and limit is 0.3. We were advised a new cat was needed. New cat arrived and was fitted. Reading went up to 0.7, so it failed even worse!

The Bongo has had new air filter, new oil recently and a new HT cap and leads a couple of years ago.

The MAF and Lambda sensors are not dead, but not sure what readings they should give, so if anybody could confirm what readings a health MAF and Lambda sensor should give out on a v6 bongo petrol that would be much appreciated.

If anyone has experienced something similar or has any more ideas as to how to fix, that would be much appreciated.

[g8dhe]

I recently had the same situation.
New Cat's. weren't available hence one from a breaker was supplied, on turning up at the garage it was rapidly noticed that there was no "brick" in the cat itself! As you can see below;

Needless to say it was returned The company were very apologetic!
I eventually was able to locate a suitable one from https://www.catman.co.uk/ which brought the emissions down to 0.21 well within spec.!
So it might just be worth checking the Cat that was fitted!!

[pikey]

Thanks Geoff. We ordered a brand new cat, as it happens from Catman in Southampton for the same reason as you - we couldn't get a new one from any of the normal Bongo part suppliers. Ours was new from them through, not refurbished as there was only £50 difference between the two so we went for the new one.

Do you happen to know what the MAF and Lamda sensor on a v6 should read on a multimeter? Catman isn't being very helpful in sorting it out, insisting on a 4 gas report before they'll do anything about it. I'd just like to rule out the MAF and Lamda sensor as being problems, but I can't see how they can be when a new cat actually makes the emissions worse!

I will ask our garage to check for the brick inside the cat tomorrow though just in case.

[g8dhe]

The O2 (Lambda) sensor, when disconnected (engine running);
Idle 0 to 1.0 volts
Accelerating 0 to 0.5 volts
decelerating 0.5 to 1 volts

The page from the Airflow sensor is below, it seems to vary according with what is measuring it hence the page image, but I suspect you will be using a normal circuit tester - multimeter.

[Bonneville]

I'd go back to basics with this one. What colour are your plugs? Does it feel like it runs rich or lean? A lean condition may show as pinking under load. Check your cam and ignition timing. Have you had a recent cam belt change? Check your compressions next.
I'm seeing a lot of this kind of thing with the petrol Bongo's. They are being maintained as if they are a modern car where things like ignition timing are fully managed by the ECU.
Bongo ignition timing is on the service schedule but rarely checked. Also, older designs are much more tolerant to cam timing alterations. The 2.0 cam wheel has 4 different positions for timing it against TDC and will run on any of them but the characteristics (including emissions) are different for each.
Any variation from stock may cause an incomplete burn and this will fail your emission test. If all of the above fails, change your O2 sensor.

[pikey]

Thanks for all suggestions.

It turned out the old cat was not faulty. There was a small leak revealed by a smoke machine. Once this was fixed the emissions dropped within range.