Help please. MOT failure on emissions.

[Graham]

My NSX just failed it's MOT today on emissions. The Lambda spec is 0.97 to 1.03 and my car was 1.072 first time and then 1.12 the second. They give them two chances. There are no warnings on the dashboard about failed sensors.
The car was off the road for 6 months in the winter and the trip to the MOT station was pretty much it's first trip out. I reckon it needs a good ragging to clear it all out inside, but now with no MOT I can't legally drive it anywhere.
I'll take the very long route on Monday to the MOT place in an effort to get the system as hot as possible but I can't think of anything else I can do.
Any ideas anyone?

[NSXGB]

Yes, book it in for the MoT and take the long route there, preferably up the motorway. Get the cats really hot and get them to check it ASAP at the station. It should be fine.

[britlude]

also give the air intake temp sensor a clean, reports that it makes a difference on NSXprime, and costs nothing!

http://www.nsxprime.com/forum/showthread.php/159564-Is-your-NSX-failing-smog-Read-this

[Graham]

OK, well there's a hint from Britlude's link to Prime, about the Air Intake Temp Sensor. As I've only ever worked on the nuts and bolts stuff and left all the engine stuff to Kaz, does anyone halve a photo of where this sensor can be found? On Prime there seems to be a conflict about whether it's on top of or below the intake manifold:-

"Bottom of the intake manifold, on the front bank under where the throttle cable is roughly and to the right of the EGR"
"The sensor is highly visible on top of the intake manifold, "

Also I need to remove the magnesium i (http://shop.ebay.co.uk/?_nkw=intake+manifold)ntake manifold cover, and the plastic fuel rail cover. Any thoughts?

I could just start taking pieces off starting at the top but I only have Sunday to do this before I go back to the garage on Monday morning. I could delay that of course but they're doing a four wheel alignment check and they said they'd shove the emissions sensor up it's exhaust at the same time.

[britlude]

here you go.... pretty straight forward, just don't drop any screws!


the sensor is on the top of the engine, front side of the inlet manifold.... just above the H of the honda logo
https://farm5.staticflickr.com/4302/36012251665_4e238bf823_c.jpg (https://flic.kr/p/WShcLM)WP_20151212_13_15_06_Pro (https://flic.kr/p/WShcLM) by jon sutherland (https://www.flickr.com/photos/152809076@N06/), on Flickr

the top cover and the front injector cover off....
https://farm5.staticflickr.com/4301/36012254265_8f1090187c_c.jpg (https://flic.kr/p/WShdxB)z2012-05-17-521800x600 (https://flic.kr/p/WShdxB) by jon sutherland (https://www.flickr.com/photos/152809076@N06/), on Flickr

looks like this.... probably filthy and covered in oil and debris
https://farm5.staticflickr.com/4328/35201550223_f9ff198b1c_c.jpg (https://flic.kr/p/VCD9tH)z2012-05-17-522800x600 (https://flic.kr/p/VCD9tH) by jon sutherland (https://www.flickr.com/photos/152809076@N06/), on Flickr

what it should look like!
https://farm5.staticflickr.com/4295/35622958450_1fbcc1706b_c.jpg (https://flic.kr/p/WgSYsN)z2012-05-17-526800x600 (https://flic.kr/p/WgSYsN) by jon sutherland (https://www.flickr.com/photos/152809076@N06/), on Flickr

[marknsx]

My Nsx has just been MOTd. Failed on emissions. Honda ran it very hot and hey presto it passed.

[Hagasan]

I'm sure it'll be far easier to run the car really hot then go straight in to the emissions test.

A few years ago I booked my car in for an MOT. I asked the garage if they would do it upon arrival at the alotted time. Of course they said yes..

When I arrived I had to wait and they finally stared about 45 mins later. Of course it failed. Now I'm running a CTSC on my car but also bear in mind that this supercharger is 50 states legal in the USA so even in California it passes the emissions test.
Based on this and even though the design is to run a little rich I fully expected it to pass.... as long as it was hot.

I said this to the mot tester although he seemed sceptical. I discussed this with the service manager and how I'd made the specific request to test the car promptly and on time...

I then took the car for a quick run up the A1M between junctions, returned, the tester hooked up and it passed!!

So as others have said... get it hot.. It might be all that's needed. If your car is standard with the cats etc and there is no engine light signalling a possible lambda sensor fault it should be fine. Just have a decent run after its hibernation....

[Nick Graves]

Lambda sensors can go off as they age and so the car could be running rich. Sooty tailpipes might be a sign...

I used to give my Prelude an Italian tune-up before the MOT, as it did use oil - early FRM bores. Always absolutely fine on the test!

[Kaz-kzukNA1]

Is your NSX first used before 01/Aug/92?

[Graham]

Hello Kaz, nice to hear from you again. Alas no, even though you were convinced that from the engine/chassis number that it's a '91, it nonetheless was registered in April '93.
Were the rules different before August '92?

[Kaz-kzukNA1]

If it was before 01/Aug/92, you need non-CAT test that looks for the CO/HC data only and not the lambda.
Your post suggested that the tester carried out the BET and not the non-CAT test so that's why I asked.

You may want pointing it out to the tester to check the spec of the engine based on the VIN.

Even if you failed the BET, that doesn't mean MOT failure.
They won't be able to find the exact match of your NSX for the combination of VIN and engine spec because it's 91 model registered in 93.
Even the VIN format for 92 model is different from yours.
Therefore, if followed the emission test screen, this should result in carrying out non-CAT test.
It's like having replacement engine from earlier model on the later spec chassis.
[Edit: Graham, if you send me an email at kaznsxcb-002'at'yahoo'dot''co''dot''jp' , I can send you a document showing the VIN and Eng no. combination for 91, 92, 93 models that may help in assisting your claim.]

If failing to convince the tester, then as others suggested, just keep the CAT really hot.
The emission test procedure is within the closed loop control region and because of the delay in the sensor as well as the in the feedback loop, several small factors will add up to hit the limit.
Old fuel doesn't help but again, keeping the CAT hot is the key.

You are allowed to drive the car even after the MOT expired as long as you can prove that you are on the way to take the MOT. You can book for MOT and ask the test station to send SMS/email/etc as the proof in case you were stopped or caught on road side camera for some reason.

Kaz

[m666 edd]

I think my NSX was first used January 1992 (It's dated in the dealer book) but DVLA lost the data at some point and it's now registered as new years eve 1992 which is a pain.

[Pride]

I think my NSX was first used January 1992 (It's dated in the dealer book) but DVLA lost the data at some point and it's now registered as new years eve 1992 which is a pain.

If that were me I would get in touch with the DVLA and insist they date it before Aug92 if you can prove it was first on the road via the service book as obviously at the moment you can't de-cat it and improve it with a performance exhaust.:(

[Kaz-kzukNA1]

Replied to your email, Graham.
Sometimes, depending on the document format, hyperlink, etc could trigger spam filter so please check your spam folder if you haven't received it yet.
Hope the documents will assist your case.

Please just keep the CAT hot.
No point in using high rpm that will force the ECU into open loop mode.
Cruising at 50 -70mph in 5th/6th gear for sometime is best as what you need is the rapid oxidation/regeneration cycles at the CAT.

Kaz

[Graham]

IT PASSED !!!!

I found and cleaned the air flow temperature sensor, thanks for the photos Britlude, cleaned the air filter as best I could with air jets, and drove along the M5 for two junctions and back before I went to the place that did the MOT. I kept the engine running all the time and he eventually, after warming up his machine, stuck the probe up the exhaust. The lambda value came into spec but the HC value was too high, even though it passed that bit on Friday. I was close to tears. On the second test the HC finally passed as well so I was happy at last. Now I can sleep.

I tried to argue that it was a '91 Kaz, but he said the rules were it had to be treated by the year it was registered. Thanks for the info though anyway. I wish there was something I could do about it. Still, lessons learned for next year.

Thanks to all who helped. That's what I like about this website. Years of experience on these cars and helpful people.

Graham

[britlude]

hurrah, glad it passed! i have the same argument every year as mine came in in '98, and is a '92 car...

[mart155]

I also have the same issue, mine is a JDM and was registered with DVLA as a 96 model but I am pretty certain it's actually a 91 car.
For starters, I have no power steering and I am sure I saw some Japanese VIN numbers listed in the distant past that confirmed my suspicions.
Does anyone know where you can find Japanese VIN number information.

[mart155]

It passed the MOT anyway but Norton Honda confirmed it was a 91 by the Vin Number.
CO was 0.011
HC was 11
Lamda was 1.004

So all is good :)