MOT failure emissions

[Anonymous]

Hi, my 2001 79000 mile roadster has just failed an MOT due to emission. I have had it serviced since the failure and it runs a lot smoother now but the emissions are still not passable. Think it was the carbon monoxide one which was 0.76ish when tested for the MOT and the max pass is 0.3. They're now down to about 0.5ish but still too high.
I know a great independant Toyota guy that services it and he is struggling to think of the reason why at the mo. He said he has never seen a roadster fail on emissions before I guess due to the number of cats it has! The next thing he is going to try is remove the oxygen sensor and clean it to see if this helps.
Perhaps unrelated but you never know it has a slight flatspot at around 4500-5000 revs. This was much worse before the spark plugs were changed but is still there a little.
My MOT has run out now so need it sorting asap.
Anyone got any ideas what could be causing the high emissions?
Thanks.

[SteveJ]

If you search, this has been covered before (several times  s;) s;)  )

Basically -

1) MAF (clean or replace)
2) O2 sensors (replace)
3) Ensure car is HOT when the test is done - go out and thrash it to the limit and then drive straight into the test bay.

Futher disucssions CAN be found using the search button.

[markiii]

I'd also be checking my precats  m http://www.mr2roc.org/phpBB2/viewtopic.php?t=11393 m

[andywood]

Doesn't sound good   s:shock: :shock: s:shock:  

I doubt very much if it would be the o2 sensor (I assume that you have not got the CEL light on?). If your guy decides he is going to clean it then just be careful as they are not really designed to be cleaned and the ceramic based sensing element is very prone to damage if taken to with wire brushes and cleaning fluids   s:wink: :wink: s:wink:    s:wink: :wink: s:wink:  

It is possible that the main CAT may be in poor condition, so it may be worth getting this checked, although if this is the case then this could be pointing to other problems.

Alot of the people on here seem to have flatspots cured by cleaning or replacing the MAF, but agan I doubt that this would be the cause of the MOT failure as you would expect to see this captured by the o2 sensors in closed loop fuelling.

There are some real experts on here so you are bound to get a better answer than mine   s:D s:D

[Anonymous]

Thanks for those quick answers.
I did find some info searching on here but nothing with the emission problems.
No CEL light on.
I did make sure the engine was nice and hot before having the reading done but didnt seem to bring them down. The garage man thinks that there may be something blocking the main cat or it may be knackered so when he takes the oxygen sensro out he's gonna have a look. Hopefully it'll be something simple. The annoying thing is the car drives very nice and also looks good too so shame it's just failing on this little thing!

[markiii]

the only thing likely to be blocking your main cat is precat material

so you need to do some reading of teh link I posted above quick smart

[Anonymous]

Sorry forgot to mention, when he serviced it I printed off the giude to gutting the pre-cats and he checked them all out. He said they were in perfect condition and showed no signs at all of deterioration.
Following on from that.....he worked in a Toyota dealer for umpteen years and still has good relationship with them. When he was in there getting the parts for my service he spoke to them about the pre-cat problem and the dealer nor himself had ever come across the problem or even heard about it! Strange!
By the sounds of it perhaps the main cat is breaking up inside and that is causing the problems.

[markiii]

the main cat is IIRC metal so unlikely

strangely no dealer in teh world has ever heard of teh pre-cat problem can you say "corporate denial"

precats can break up from teh top or teh bottom, did he unbolt teh nanifold to check them?

[Anonymous]

Im not sure how he checked them to be honest but he was confident there were no problems with them.
If it was just the dealer then I would believe the denial thing but the guy I know is a friend of the family and works for himself so would have nothing to gain from not admitting the fault. Maybe the garage are sworn to secrecy even to him!

[andywood]

when you have done the futher checks and hopefully (very soon) fixed the problem, it would be good to know what the problem was. Make sure you update us all   s:wink: :wink: s:wink:

[Anonymous]

Yeah no probs will.
Just reading some other posts using the "search" and one possibility was oil getting into the cat and contaminating the o2 sensor. When it was serviced the other day the garage noticed that there was very little oil in the engine! He was shocked and gave me a good telling off for not checking it regularly! The exhaust never smoked or anything though so no signs of burning oil and no leaks under the car so where would the oil have gone?! This might be not related at all though.
I'll keep you posted, unfortunately he cant have another look at it until next Thursday!
Im was having the wheels refurbished then but that'll have to wait until the week after, I guess an MOT is more important than the corroding paint on the wheels!

[markiii]

oil can only get in teh cat via teh exhaust and hence via teh precats

and a typical symptom of precat failure is a sudden loss of oil.

so now we have

1. sudden loss of oil
2. potential main cat blockage
3. power fluctuation at 4500

guess what my money would be on

not being funny, but did you read teh link I posted?

[Anonymous]

get the manifold off and check the pre cats now! tbh though i fear its to late.

[Anonymous]

Yes, I read the info from the link, I actually printed it off and showed the guy who read through it.
I just called him to ask about the pre-cats and he didnt remove the manifold but will do when I take it in to him next Thursday.
The strange thing is to me though if it is the pre-cats which are the problem would the car run progressively more rough until eventually just grinding to a halt?
Since he serviced it and replaced the plugs etc 2 days ago its running silky smooth and seems fine.

[roger]

If the precats don't get in the engine it will be like normal until you get to 4,000ish revs when the pressure starts them to block the main cat.

If the precats get in the engine, well it depends how quickly damage is done. It might be a fair time, or you might just go BOOM.

Should just warn you, they WILL eventually get in the engine unless you do something PDQ and have a bit of luck on your side.

[Anonymous]

Thanks.
In that case in the mean time I presume it would be best to drive it at sensibly low revs until sorted and obviously preferable to not drive it at all?

[Anonymous]

not at all. you may still be lucky, i hope so, but the more you drive it the more likely it is to go bang.

[Anonymous]

Fingers crossed then! I like living life on the edge!........the edge of huge expense!
I've decided I hate cars!....trouble is its so sunny out today I feel the need to put the roof down and drive!

[Gazz]

Why ask for advice and then completely ignore it wasting everyones time ?

[Anonymous]

Why ask for advice and then completely ignore it wasting everyones time ?

Chill out! Im only kidding!

[mr2mark]

Hi .... I am an mot tester ...... Have you got the actual readings of the cat test ?  Just if the reading of the co's was .76 then .50 it looks like it should of been ok (just warming up) ... let me know the exact result of every reading ..... hc's... co's.... and lambda readings ............ waiting to hear..........

[Anonymous]

Hi .... I am an mot tester ...... Have you got the actual readings of the cat test ?  Just if the reading of the co's was .76 then .50 it looks like it should of been ok (just warming up) ... let me know the exact result of every reading ..... hc's... co's.... and lambda readings ............ waiting to hear..........

Thanks Mark, right....
The failure said "Exhaust emissions carbon monoxide content after 2nd fast idle excessive"

The amounts were

First idle test
CO 0.703 FAIL MAX limit 0.3
HC 17 Pass MAX limit 200
Lambda 0.982 Pass

Second dast idle test
CO 0.746 Fail MAX limit 0.3
HC 8 Pass MAX limit 200
Lambda 0.980 Pass

Natural idle test
CO 0.082 Pass MAX limit 0.5

Overall exhaust emission test FAIL

The guy that serviced the car after changing the plugs, fuel filter and putting in a full cleaner to the tank has brought the CO down to about 0.5ish (just above).

Any help appreciated. Thanks a lot.

[mr2mark]

Has the printout got the engine temperature on ? it might say something like "temp gauge shows warm" or "cooling fan cut in" etc. If your cat was working properly it will be hovering between around 0.00 + 0.03. This is if the cat was "conditioned" as we call it (warmed up basically).
 A catalytic converter either works or doesnt work.... Ive seen the odd occasion where the COs go up and down all over .... this is normally when the cat is on its way out.  

 p.s where you based ?? anywhere near newcastle and I can check the emissions for you.

[Anonymous]

I'll grab the bit of paper from my car in a bit and get back yo you, cant remember what it said now about the temperature.
Unfortunately Im in Southampton.
I'll let you know what it says.
Thanks.

[Anonymous]

No mention of temperature on the results form.
I should imagine that it wasn't at hottest as it was parked for a while before the MOT was carried out.