Just failed the MOT on the emissions 1992 N/A manual.

Any advice on a good garage in the Bucks/Beds area to get it checked out and adjusted.

CATS are in place.

Thank you

check the print out for the emissions, did they put it through as a non cat test? and also check to make sure its actually been tested as a 300zx, if its gone through as a cat test then they need to retest it, these cars are NON cat test.

Thank you for the prompt reply.

Not sure which test but will check.

However , was showing CO 5% so a fail either way ??

I your car as standard or has it had any performance tweaks? If so, may be worth listing them.

Personally, I would start with the basics, such as air filters and ignition timing.

Also, may be worth checking base idle and TPS settings, all of which may have an adverse affect on emissions.

A good place to start at least.

As Ian stated, the 300zx or fairlady is not on the MOT emissions database and therefore has to be tested as a pre cat, regardless whether you have them fitted or not.

 

As long as its not smoking like a chimney, it will pass a precat test as is.

As Ian stated, the 300zx or fairlady is not on the MOT emissions database and therefore has to be tested as a pre cat, regardless whether you have them fitted or not.

 

As long as its not smoking like a chimney, it will pass a precat test as is.

 

So he will not have to improve the CO 5% reading?

I was lead to believe that the alternative test required a reading of below CO 3.5% .

Looks like I am getting the run-around from my current MOT tester, time to go to Zedworld me thinks.

5% is too high regardless - redwine is correct, non cat test limit is 3.5% CO

Any advice on a good garage in the Bucks/Beds area to get it checked out and adjusted ?

So building on this question then what is going to be the most likely source of high C0% then? for anyone else who reads this in the same situation, apart from pulling the pipe off the balance bar to get the reading down, how would you go about curing the issue? and what are the causes.

 

One further question, but to the OP, do you have a cat back stainless steel system, or is it a complete OEM exhaust including cats, reason i ask, cats could have been gutted if its a aftermarket rear system. 5% seems way too high with cats on unless they are fubar.

So he will not have to improve the CO 5% reading?

I was lead to believe that the alternative test required a reading of below CO 3.5% .

Looks like I am getting the run-around from my current MOT tester, time to go to Zedworld me thinks.

 

I was talking bout the zed generally regarding cat test and emissions, i didnt look at the CO reading in answer to the OP ( apologies there) merely mentioning that some garages unfamiliar with the zed tend to fail on emissions.

 

His EGR is likely fubarred or as Ian stated, cats may be gutted.

on my MOT yesterday during the sniff test the guy held the motor at 3000rpm and just before timeout the cats got hot enough and kicked in and cleaned the gasses up. Tester told me the cats need to be upto temp before they start cleaning the show up so maybe your motor was not brought upto temp before the test.

mine was quite high at idle, fully decatted. however it passed, was fine off idle. however I had loadsa shitty oil burning off in my exhaust from where my turbos had blown, it ran out of mot while I was fixing it so had no choice but to get it tested before it had fully burnt off.

 

- - - Updated - - -

 

whats your base idle and is adjusted correctly?

also another thought if you've got a boost leak you could be loosing metered air and creating a rich mix.

Thank you for the prompt reply.

Not sure which test but will check.

However , was showing CO 5% so a fail either way ??

 

Was this CO 5% recorded at idle or at a higher rpm?

The reason I ask is, I believe your car, due to it's age should only be tested at idle.

also another thought if you've got a boost leak you could be loosing metered air and creating a rich mix.

 

only a major boost leak would cause that, and that would be very noticeable as the car will want to cut out a lot and blow lovely nice black soot out the rear.

 

he could always pull the small pipe off the balance bar and hide it somewhere, then take it, that would get his reading down past 5% but doesnt really solve what the cause is.

 

SO what would the cause be if lets say, No cats, all boost pipe work is tight and no leaks. no one seems to be mentioning what could cause it, hence be able to fix it for him.

I your car as standard or has it had any performance tweaks? If so, may be worth listing them.

Personally, I would start with the basics, such as air filters and ignition timing.

Also, may be worth checking base idle and TPS settings, all of which may have an adverse affect on emissions.

A good place to start at least.

 

As I mentioned earlier in the post, I believe the first place to start would be with the basics.

The fundamental reason for high CO % is either low air to fuel ratio, (ie too much fuel and too little air) A close second may be down to poorly burnt fuel mixture that could arise from poor ignition timing.

In addition to these there are more complicated possible causes, such as valve timing etc' all of which collectively or singularly could be the problem. I think a thorough check of these initial setting would be worth a try. Unfortunately, it maybe a process of elimination I'm afraid.

My 97 N/A has failed on emissions, it passed at idle but at 2600 it failed with co 0.51% and lambda 1.099 is it because I have a after market cat back exhaust which is ultra loud as it failed on both banks although the second bank was a bit lower at co 0.07 lambda 1.070 would putting the original catback exhaust bring the figures down? or is there something else wrong

Just failed the MOT on the emissions 1992 N/A manual.

Any advice on a good garage in the Bucks/Beds area to get it checked out and adjusted.

CATS are in place.

Thank you

as its an import there is no uk legislation to confirm its the original engine therefore it is on paper poss that it is not the original engine ;)

and as that is the case and it is that the replacement engine was from an earlier car say 1990 then it does not require an emissions test on the newer stricter emissions and falls in to the basic one like any pre 92 car ;)

so tell them its had an engine fitted out of a 1990 and you dont even need to have cats fitted this applies to all imports and uk cars also in some aspects

mot tester may ask for a letter of you just to confirm this for his safe being ;)

MMM it looks like I have probably got a dodgy spark plug or something on one bank then but how do I lower the lambda reading?

Sorry to jump your post Bill

after phoning up the garage they only test 1bank so I passed the co2 with the second pass yippee but the lambda is still1.070 so will the original exhaust cure this or is it the balance pipe trick?

Sorry to jump your post Bill

after phoning up the garage they only test 1bank so I passed the co2 with the second pass yippee but the lambda is still1.070 so will the original exhaust cure this or is it the balance pipe trick?

 

Your exhaust shouldn't be the issue, barely any of us have the stock system these days. FOR two reasons, A most have opted to get the gains from a catback the stock system is very restrictive, B. the reason they made that option is the original has rotted away and the OEM replacement if you could get hold of one is seriously expensive.