Just failed MOT emissions advice needed

Good evening everyone, im hoping that i can benefit from your combined experience and shed some light on what may be at fault.

My car is a 93N/A Jspec.

Ive just had the car MOT`d and it failed on emissions. I have several questions about this

1) Ive looked back at previous MOT emissions readings to see if i can find a pattern that may assist you in identifying the cause of the failure/high emissions and i list them below

DESCRIPTION DATE SPECIFICATION ACTUAL VALUE PASS/FAIL

CO Feb 2005

HC Feb 2005

Lambda Feb 2005 0.97 - 1.030 1.015 PASS

CO Jan 2007

HC Jan 2007

Lambda Jan 2007 NOT EVEN ON MOT EMISSIONS SHEET!!

CO Jan 2008

HC Jan 2008

Lambda Jan 2008 0.97 - 1.030 1.023 PASS

CO Jan 2009

HC Jan 2009

Lambda Jan 2009 NOT EVEN ON MOT EMISSIONS SHEET!!

CO Jan 2010

HC Jan 2010

Lambda NOT EVEN ON MOT EMISSIONS SHEET!!

CO Jan 2011

HC Jan 2011

Lambda Jan 2011 0.97 - 1.030 1.063 FAIL (again how did it pass last year?)

CO Jan 2012

HC Jan 2012

Lambda Jan 2012 0.97 - 1.030 1.038 FAIL

PS: they actually did 2 x fast idle checks for emissions in 2011 and 2012 and both results were similar each year.

It looks like my CO emissions have been rising gradually since i bought the car in 2005 (apart from the spurious 0% result in 2008). Why would my emissions have risen over the years? What corrective action is needed to get the car back below the 0.3% limit? (replace Catalytic converter?)

2) Why has the specification for emissions (CO) changed since I bought the the car in 2005. From 2005 to 2012 the specification on the MOT emissions slips has changed from . WHY?

Any advice would be welcome (especially a good garage in Reading)

Sorry the formatting has come out all messed up when i clicked submit!!

Not realy sure but did they test it specificaly to your cars year

Im sure somebody with more know all will post soon

Not realy sure but did they test it specificaly to your cars year

Im sure somebody with more know all will post soon

Dont know, recall a conversation with the MOT tester a few years back when the spec was 3.5%. he said that he couldnt find the Supra model (N/A) on the DVLA emissions register and hence they just used a "capture all" massive spec of 3.5% in such cases. bearing in mind that conversation, im wondering if they have mistakenly used the emissions spec for a UK TT car on other years?

THIS THREAD may be worth a read.

Does the car have both catalytic convertors fitted?

Likely cause of the poor emissions are duff oxygen sensors (2 on the NA Supra), see HERE for more info. New O2 sensors should improve the emissions and make a noticeable improvement in the mpg's.

89465-19615 Toyota Oxygen Sensor x 2 - 2JZ-GE

THIS THREAD may be worth a read.

 

Does the car have both catalytic convertors fitted?

 

Likely cause of the poor emissions are duff oxygen sensors (2 on the NA Supra), see HERE for more info. New O2 sensors should improve the emissions and make a noticeable improvement in the mpg's.

 

89465-19615 Toyota Oxygen Sensor x 2 - 2JZ-GE

thanks Nick.

Actually i think only 1 cat is fitted. If i recall correctly from last time i visited the garage and saw it on the ramps the cat on the horizontal part of the exhaust appeared to have been cut/welded suggesting to me that maybe it had been hollowed out or something like that. Bearing that in mind do you think it will be cats or O2 sensors or both? (or something else?)

thanks Nick.

 

Actually i think only 1 cat is fitted. If i recall correctly from last time i visited the garage and saw it on the ramps the cat on the horizontal part of the exhaust appeared to have been cut/welded suggesting to me that maybe it had been hollowed out or something like that. Bearing that in mind do you think it will be cats or O2 sensors or both? (or something else?)

It should pass with only 1 cat fitted, some pass without any cats fitted.

Oxygen sensors only have a certain life span and need replacing every few years (I think Toyota state they should be changed every 50K km's from memory), the link above explains how to test them. Once they are worn the ECU defaults to a rich fuel mixture which effects the emissions, causes poor mpg's and slight loss of power. New O2 sensors are not cheap but should pay for themselves in fuel savings very quickly.

...2) Why has the specification for emissions (CO) changed since I bought the the car in 2005. From 2005 to 2012 the specification on the MOT emissions slips has changed from . WHY?...

CO Jan 2012

HC Jan 2012

Lambda Jan 2012 0.97 - 1.030 1.038 FAIL

However... if it's a '93, according to the flowchart it should have been either tested to vehicle-specific limits or given a non-cat test, but they have used the default CAT test limits. Seems to me that the fail is er... a fail.

Because of this flowchart, followed by this flowchart, and different interpretations of the rules.

 

.

Thanks mate you guys are fantastically knowledgeable. So basically according to those charts it progresses to page 9 after the fail, they cant find an exact match and so they should have used 3.5%?

Brett, correct. They've tested your car using the wrong category. You should be tested as a non-CAT as mine is every year (and as they have done in 2007/2009/2010) and it should pass easily, esp with 1 cat fitted. Mine passes with no CAT's although I do use a "friendly" tester.

Brett, correct. They've tested your car using the wrong category. You should be tested as a non-CAT as mine is every year (and as they have done in 2007/2009/2010) and it should pass easily, esp with 1 cat fitted. Mine passes with no CAT's although I do use a "friendly" tester.

JACKPOT - cheers for confirming that mate.

Anyone got any ideas on how i approach the MOT station to explain all this? Im thinking of printing the flow charts of and going through it with them, but dont want to sound insulting/demeaning.

Just tell them to read the damn manual. It's all pretty clear in there.

Just tell them to read the damn manual. It's all pretty clear in there.

Further to the previous advice, it would be a good idea to empty a bottle of injector cleaner into a quarter tank of fuel and give it a good thrashing. I can personally recommend Wynn's as very effective in cleaning some of the coke out of the runners and generally cleaning up the exhaust. Amazing stuff. Purple bottle. Lucas is also good. They probably all are.

After 19 years, you're going to have some serious carbon deposits in the combustion chambers so if all else fails, a de-coke will sort it out. Basically a cylinder head rebuild and clean including shim adjustments if necessary and valve touch up. Specifically, the valve stem seals should be changed if the car puffs blue smoke on startup. That will clog your O2 sensor like nobody's business so best get it sorted asap.

I'd say that you should be fine as you are with a re-test, if that was the problem, as the hydrocarbons are still remarkably low for a car of that age but definitely chuck a bottle of injector cleaner in as extra insurance. You might not notice any Hp improvement but it will definitely clean up the emissions significantly unless it's just been rebuilt.

I had the exact same problem last year with my NA mate.

I went back with this info I gained off of here and he just printed off a MOT certificate and all was fine.

My dilemma now is do I go back there because he knows the car or do I go some where else because I pissed him off last year and he'll fail it on something else this time

I had the exact same problem last year with my NA mate.

I went back with this info I gained off of here and he just printed off a MOT certificate and all was fine.

My dilemma now is do I go back there because he knows the car or do I go some where else because I pissed him off last year and he'll fail it on something else this time

As far as I can tell his car was tested to those standards and it failed. The CO2 was way over 0.3% hence why it failed the test.

I would try the lemon cure on the O2 sensors to see if that clears up your problems.

On a different note, mine failed the test last year, changed the coil pack connectors/ new plugs/ sorted a leaking cam cover gasket that had dumped some oil into the sparkplug orifice on #6 and then passed with no problems. also ran better even though there was no discernible missfire before.

They always test mine under the 3.5% rule even though it would pass the 0.3%, this is with 1 aftermarket 'race' cat on a '95

good luck

R.

As far as I can tell his car was tested to those standards and it failed. The CO2 was way over 0.3% hence why it failed the test.

 

I would try the lemon cure on the O2 sensors to see if that clears up your problems.

Hi Scott. It was over 0.3% (was about 0.5%), but the important point is that 0.3% is the incorrect spec to use according to others on here. They should have used 3.5% as the car is a 93Jspec N/A.

Ive since visited the garage and they have agreed that they tested it incorrectly, so now i just need to get get it back in for a retest using the proper specification. (i wouldn't mind all this hassle if it wasn't patently obvious that its a 93car because its an L plate and even said that its year of first use was 93 on the MOT failure sheet!!, For some unknown reason they tested it as a 95> car)

Hi Scott. It was over 0.3% (was about 0.5%), but the important point is that 0.3% is the incorrect spec to use according to others on here. They should have used 3.5% as the car is a 93Jspec N/A.

 

Ive since visited the garage and they have agreed that they tested it incorrectly, so now i just need to get get it back in for a retest using the proper specification. (i wouldn't mind all this hassle if it wasn't patently obvious that its a 93car because its an L plate and even said that its year of first use was 93 on the MOT failure sheet!!, For some unknown reason they tested it as a 95> car)

Ahh I'm with you now. Reading the snippet posted 0.3% is where you won't find any issues but clearly that was a little misleading

Gld you're getting it sorted