R33 GTR Emissions Fail...

[DaveR]

Took my car for an MOT this morning and failed its emissions...it has High C02, Low Lambda reading and the N2 (think thats what he mentioned) was a little erratic but within pass paramters. I bought the car de-catted but had it refitted and the original Lambda sensor was taped up under the car and refitted. During the trip to the MOT station I did notice that there seemed to be a little hesitation before the power came on.

They seemed to think it could be split or ill fitting pipe or it could be the lambda sensor gone or it could be a combination. Anyone else have any experience of failed emissions and how to get it through? Any specific areas to check for split pipes or ill fitting pipes? Any advice would be appreciated...

Cheers
Dave

[Mookistar]

lambda, if strapped up under the car for an extended period is probably fooked

mook

[DaveR]

Thanks for the quick reply...
I bought the car a couple of months ago....not driven until now so god knows how long it was strapped under there!!! Any idea the best place to get a new one?

[Mookistar]

any of the tuners should be able to sort you out.

[DaveR]

would this also explain what feels like a little hesitancy when you put your foot down? I assume the engine management can't cope if the sensor is not working correctly!!

[Mookistar]

if there is no sensor connected, then engine will compensate and overfuel slightly

if there is a sensor connected thats reading wrong, it could be running extremely rich or lean at low revs. defo worth checking as lambdas are quite sensitive and won't like being exposed to the elements

mook

[Moff]

Lambdas should be changed every 60k. You have 2 on your GTR on the down pipes. If they are old and not working properly, which is likely then the emission will be naff and you'll be chewing through fuel.

The one going into the de-cat will not affect the running of the car. Most people tape these up out of the way when they fit de-cats (I took mine out)

[DaveR]

what does the sensor in the cat do then if it doesn't affect the running of the car? Car has 65000 so probably never had any new sensor before...where is the best place to buy? Any way of telling if they are knackered or is it one of those where you only know if you replace them?

I am leaning more towards the sensors being knackered with a high Co2 and low Lambda (haven't got the sheet but they said CO2 2.083% and the lambda was 0.76) although they did mention could be a split pipe or something not secured...which ones are best to check if that were the case?

[Moff]

I think its a warning sensor (could be wrong) if ECU picks up the exhaust is 50 million degrees, car goes into limp home mode.

Linky for Lambda

Just Lambda, Skyline lambda sensors, Bosch and NTK zirconia and titania sensors by post

[OO__OO]

Yep, sensor near the CAT is just a temp. sensor. Your lambda reading should be between 0.97 & 1.03. Your reading of 0.76 means it's too rich & pushing up the COs. Check for leaks on exhaust manifold / turbos. If its sucking air in the lambdas will thing the mixture is too weak & richen it up.
Hope this helps.
Phil