O2 sensor, cat, or...?

[havoc]

Car's just failed the MOT on emissions - some very big numbers seen, but no real smell from the exhaust.

Car seems to run fine - a little lumpy at the low-end (<2,000rpm), but that's it.


I've got the above two items as potential culprits, but before I go further, does anyone have any other bright ideas.

Also, can anyone recommend a supplier for a high-flow-cat?

Cheers,

Martin.

[AR]

Car's just failed the MOT on emissions - some very big numbers seen, but no real smell from the exhaust.

Car seems to run fine - a little lumpy at the low-end (<2,000rpm), but that's it.


I've got the above two items as potential culprits, but before I go further, does anyone have any other bright ideas.

Also, can anyone recommend a supplier for a high-flow-cat?

Cheers,

Martin.


Did you heat it up really well?

If you need a pair of cats to pass MOT you can borrow mine.

Cheers,

AR

[havoc]

Yeah, a mate took it to a garage he knows well (has an account with them), and they took it out for a blat and then straight back on the machine while hot, but the HC and CO2 figures were still sky-high.

Problem is it's an OBD-I car, which makes diagnosis a little more difficult. I'm inclined to get a pair of O2 sensors from Matt (VTECdirect), get them fitted, and see what happens, but I'll bear the offer in mind if that doesn't work - thanks very much! :)

(Out of interest, I swore I could only see one central cat on mine (3.0) - am I missing something?!?)

[NSX 2000]

(Out of interest, I swore I could only see one central cat on mine (3.0) - am I missing something?!?)

Yes there should be two! (one for each bank)

[amo]

before you spend any money mate give it another good run really good might be just wot she needs

thx amo

[havoc]

before you spend any money mate give it another good run really good might be just wot she needs

thx amo

Oh, she gets them regularly! ;o)


...and I'm now off to crawl under the car and look at cats...

[Nick Graves]

Given that some S2000 will pass with a decat, I'd be surprised if the cats themselves have gone down.

If there's no CEL or other symptoms (they're all lumpy <2K - it's the wrong crank angle) then I'd suspect the λ sensors. There are four, IIRC.

Good luck getting the buggers out...

[AR]

There are four, IIRC.

Good luck getting the buggers out...

Not the case on the OBDI

You can get 02/Lambda replacements quite cheap if you are willing to splice the cables.

[Senninha]

IIRC only two on the NA1

Re CATS, if this is what you need, two options I know of are the Prospeed high flow, contact Brian on NSX Prime vendor section. These work fine on all pre LEV cars and fit perfectly.

Random Technology is another option and I think can be purchased via SOS.

Good luck

Paul

[havoc]

If there's no CEL or other symptoms (they're all lumpy <2K - it's the wrong crank angle) then I'd suspect the λ sensors. There are four, IIRC...

Yep, all the data so far is pointing towards them
- HC not high-enough for cat-failure, apparently.
- They're Kaz's first suggestion.
- And a few dozen threads on here and Prime can't be coincidental...

I'm going to start with swapping the two sensors out (a friend has very kindly volunteered himself), and see what happens...

Thanks for the advice,

M.

PS - can't believe I didn't put this in Technical...wasn't thinking straight at lunch.

[AR]

I can suply Hi-Flow cats as well if needed with or without O2 bungs. UK made stainless and lifetime warranty.

[Chris B N]

Hi Martin,
my NAI ( 97 Auto)failed last year on emissions CO levels were just over the 0.3 limit
new plugs sorted this and the car ran much better.
It failed again this year on emissions with CO levels at 11.5%
had it checked, one O2 sensor not working at all, the other could not make it's mind up
Got new sensors from Andy at VTEC, also decided new plugs would not go amiss.
Passed with very low CO levels
Hope this helps
Chris BN

[AR]

Hi Martin,
my NAI ( 97 Auto)failed last year on emissions CO levels were just over the 0.3 limit
new plugs sorted this and the car ran much better.
It failed again this year on emissions with CO levels at 11.5%
had it checked, one O2 sensor not working at all, the other could not make it's mind up
Got new sensors from Andy at VTEC, also decided new plugs would not go amiss.
Passed with very low CO levels
Hope this helps
Chris BN

What fuel are you using? Are you using the car hard enough?

Cheers,

AR

[Chris B N]

Using Shell 99 Octane,
she gets driven both gentle and hard and is very rarely switched off without being fully warmed up. Need to put the smile on my face :) at least once a week even if only for 10 or 15 miles.
Chris

[havoc]

Chris,

Thanks very much for that - pretty much the route I'm going down - just ordered two sensors from VTECdirect, will then see what the plugs look like - only 2y.o. and 10k miles so hopefully still OK.


And I echo your last post entirely (except mine tends to get BP Ultimate due to where garages are near us). Even use it to go to work in once a month or so, just so I can take the long way home! :)

[lenco12]

Did you heat it up really well?

If you need a pair of cats to pass MOT you can borrow mine.

Cheers,

AR
Yeah, a mate took it to a garage he knows well (has an account with them), and they took it out for a blat and then straight back on the machine while hot, but the HC and CO2 figures were still sky-high.

Problem is it's an OBD-I car, which makes diagnosis a little more difficult. I'm inclined to get a pair of O2 sensors from Matt (VTECdirect), get them fitted, and see what happens, but I'll bear the offer in mind if that doesn't work - thanks very much! :)

[Nick Graves]

Are you up n' running again, Havoc?

[havoc]

Just back from holiday - 2 new O2 sensors fitted, and it passed with flying colours. Very glad it wasn't the cats, just need to go pick her up and see how she drives now - hopefully she'll feel a little more responsive.


(BTW - how did I post as 'lenco12' above?!? )