Excessive co2 content ? mot fail

UK forum for general and technical discussion about the Z3 roadster
Post Reply
warhammer23
Joined: Sun 16 Feb, 2014 22:28
Posts: 62

  BMW other

Excessive co2 content ? mot fail

Post by warhammer23 »

Hi there.

My 1.9 from 1997 with 153k miles failed the MOT for "excessive co2 content at idle" and "2nd fast idle".

The numbers are all over the place and it's weird because no codes, brand new CAT and o2 sensor from 2 years ago.

These are the numbers:

-fast idle - 7.44 % (0.30 % limit)
-HC - 349 ppm (200 limit)
-lambda - 0.806

-2nd fast idle - 7.71 % (0.30 % limit)
-HC - 402 ppm
-lambda - 0.798

-natural idle - 7.29 % ( 0.50 % limit)

So wow, do i have a steam locomotive running on human souls? :)

They didn't check the oil temperature though.
The car is a daily driver, mostly short trips but at the weekend it gets its legs stretched.
It was at optimal oil temperature and they put it straight in and today wass 20 degrees C outside so that should be good.

They said that he wanted to have a look at the ECU (?) but to have a diagnostic check (45 quid).
Wanted to have a 2nd opinion.

Any input is of great help. Thank you.
therealdb1
Joined: Tue 25 Jun, 2013 21:47
Posts: 263

  Z3 roadster 2.0

Re: Excessive co2 content ? mot fail

Post by therealdb1 »

Hi, I would really worry if you had that much CO2 in your exhaust emissions.
I take it you mean CO?
That's not your only problem by the looks of it as there seems serious combustion issues to resolve.
Have you checked the spark plugs to see what condition they are in? The kind of deposits on them and the electrode condition may indicate if your engine is burning oil through the valve guides or if it is running excessively rich for example. To me the high HC is likely to be burnt oil or unburnt fuel.
Just because the Lambda sensor was replaced 2 years ago doesn't mean it is ok now. That could do with looking at to check its response as it could be contaminated from the other problems.
Before getting all electronical and putting diagnostics on ecu's and O2 sensors do some basic mechanical checks.
Look at the spark plugs - post a photo of them on here if unsure.
Have a look at the air filter to ensure that is not blocked.
Check any breather hoses that go to the induction side to make sure they are not full of oil and the engine is ingesting it that way.
Without seeing the car it is difficult to be specific but it is all too easy to blame the bits we don't fully understand before inspecting the bits we do.
Incidentally I've never known an MOT tester to check the oil temperature but your engine is so far out of specification it wouldn't make any difference anyway.
Good luck let us know how you get on.
User avatar
pingu
Joined: Fri 30 Apr, 2004 16:01
Posts: 3412

  M roadster S50

Re: Excessive co2 content ? mot fail

Post by pingu »

I needed to have two MOTs last month (*), but the first had 0.198% CO and 58ppm HC, the second test had 0.010% CO and 29ppm HC.

The reason for the low readings on the second MOT was that I had just taken the car on a 600 mile blast. So, blasting the car around at above 5000 rpm clears out any cr@p in the engine.

Make sure that your plugs are correct and in good order, your oil is clean and that your air filter is clean, and rag its tits off.



(*) because the car failed on brakes and the garage couldn't retest as they were on holiday.
Pingu
Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2136

  Z3 roadster 1.9

Re: Excessive co2 content ? mot fail

Post by Del »

Those CO readings are extremely high - ignoring any possible problem with the Cat - high CO denotes a very rich mixture and high HC an incompletely burnt mixture. What is the fuel consumption like on the car and what colour are the spark plugs?
User avatar
Davejue1
Joined: Sun 22 Sep, 2013 07:25
Posts: 1249

  Z3 roadster 2.8
Location: Mansfield

Re: Excessive co2 content ? mot fail

Post by Davejue1 »

Mines failed on co2 readings. The limit is 0.2%. Mine was 0.54%. I've been advised by more than one its most likely to be the cat. Pricing up replacements at the moment including maybe changing the whole system for a stainless. Lambda sensors are also high on the culprit list. Just had a inspection2 done but the car has only done 1500 since last mot. Gave it a good blast before taking it in and it also had cataclean pumped through as well.
Image

"Growing old is mandatory, growing up is optional!"
warhammer23
Joined: Sun 16 Feb, 2014 22:28
Posts: 62

  BMW other

Re: Excessive co2 content ? mot fail

Post by warhammer23 »

Yes i will try to check everything mentioned here what i can and the rest when i go to a full diagnostic check in 2 days because i want it sort it out. Thank you again and will come back with news.
Mugs
Joined: Wed 07 Aug, 2013 01:26
Posts: 341

  Z3 roadster 1.9

Re: Excessive co2 content ? mot fail

Post by Mugs »

if it turns out to be CAT related, i have a brand new aftermarket one, still in the packaging that i am going to sell for cheap.
Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2136

  Z3 roadster 1.9

Re: Excessive co2 content ? mot fail

Post by Del »

To put your CO readings into perspective, old cars registered before 31/7/1986 (obviously with no Cat) are allowed a MOT limit of 4.5%. Yours are over 7% :shock:
User avatar
Davejue1
Joined: Sun 22 Sep, 2013 07:25
Posts: 1249

  Z3 roadster 2.8
Location: Mansfield

Re: Excessive co2 content ? mot fail

Post by Davejue1 »

Mugs wrote:if it turns out to be CAT related, i have a brand new aftermarket one, still in the packaging that i am going to sell for cheap.
How much do you want?
Image

"Growing old is mandatory, growing up is optional!"
User avatar
Robert T
Site Admin
Joined: Mon 12 Jun, 2006 10:35
Posts: 10170

  Z3 roadster 1.9
Location: Cheshire

Re: Excessive co2 content ? mot fail

Post by Robert T »

Del wrote:To put your CO readings into perspective, old cars registered before 31/7/1986 (obviously with no Cat) are allowed a MOT limit of 4.5%. Yours are over 7% :shock:
That does tend to indicate that either they put sniffer into a badly maintained gas boiler or that there is something seriously amiss with the fuel/air ratio that the car is running on.

It would be interesting to see what my Sprite actually produces, as the only emissions test it has is a visual one, and even then it is technically exempt and I only take it for one so I have a piece of paper to wave in front my insurer.

Having no warning lights on on the dashboard does not mean that the car has not logged any error codes. When I had a camshaft sensor fail, it logged codes, but did not show a warning light. I would say that there is a problem with any of the following: Lamba sensor(s), MAF or cat. If you are getting incomplete ignition on one cylinder, I would have thought that you would be able tell it was running rough, so I am suspecting something that affects all the cylinders. Having said that, it could also be burning oil, which would certainly increase the hydrocarbons - is it using much oil?

We may be able to find you someone to do you a quick diagnostic check if you let us know whereabouts you are.

Cheers R.
Arctic Silver '99 Z3 1.9 & Black '59 Frogeye 1275cc
Image
warhammer23
Joined: Sun 16 Feb, 2014 22:28
Posts: 62

  BMW other

Re: Excessive co2 content ? mot fail

Post by warhammer23 »

That's why i am surprised.
No oil usage, no codes, no black, white or blue smoke, nothing.
The engine idles nice and smooth, pulls very good, nothing shakes.
Good gas milage stayed the same since i got it in January.
Air filter is ok .. oil still looks good (not black) will change it as a preventive. It's so wierd, the car and engine runs very good no sign to me that it had any problems.
Like i said will come back with news later on.
therealdb1
Joined: Tue 25 Jun, 2013 21:47
Posts: 263

  Z3 roadster 2.0

Re: Excessive co2 content ? mot fail

Post by therealdb1 »

There is another possibility if the car is running as well as you say it is...
When I took my daily driver Volvo for its first ever MOT when it was just 3 years old it failed on emissions at my local MOT station.
I took it back to the stealer where I brought it brand new and they said "these never fail emissions." They put it on their analyser and 10 minutes later I had a perfect emissions check.
I took this evidence back to the garage that had failed my car several days earlier and he admitted that his analyser had gone faulty and every car that he had tested in the intervening time had "failed" on emissions.
Moral of the story. Take the car to another MOT testing station and get a second opinion on what is exiting your exhaust pipe because with the sort of figures that you have been given it should be running like a 50 year old London taxi that has never been serviced in its lifetime! If it passes somewhere else you have a ticket and you can go back to the first place and tell them that their equipment is in need of attention and get a refund. If you get the same result then obviously more investigation is required and it has only cost an MOT fee to confirm but at least you will not have to spend £'s changing parts unnecessarily.
That's what I would do as I have done it before!
warhammer23
Joined: Sun 16 Feb, 2014 22:28
Posts: 62

  BMW other

Re: Excessive co2 content ? mot fail

Post by warhammer23 »

Exactly as i said on Thursday i booked another test and will know for sure if it's me or like in your case.
Vince70
Joined: Sun 08 Mar, 2015 12:51
Posts: 57

  Z3 roadster 1.9
Location: Battle

Re: Excessive co2 content ? mot fail

Post by Vince70 »

Before taking it for its new mot throw a bottle Cataclean in it and get the car upto temp then give it a bit of an Italian tuneup beforehand.

Another problem could be is if you've had an aftermarket Cat fitted to your car and you've gone for a cheap one your lucky if it normally lasts a year as there normally crap quality as I found out on my old 1993 Audi Cab.

The first one lasted 18 years without a problem then it had two cheap ones after that which only lasted a couple of years each.
warhammer23
Joined: Sun 16 Feb, 2014 22:28
Posts: 62

  BMW other

Re: Excessive co2 content ? mot fail

Post by warhammer23 »

Yeah...

The cat self-destructed. Just my luck before the MOT. And as i reached the service today i could hear rumbling underneath the car. It was on its last breath.

Ordered a new one and they will fit it tomorrow.

Hopefully that would be it.

Will come back again with news if i pass the mot - btw, also with the new cat, does it need some break in i mean some good highway runs as well?
warhammer23
Joined: Sun 16 Feb, 2014 22:28
Posts: 62

  BMW other

Re: Excessive co2 content ? mot fail

Post by warhammer23 »

All sorted now.

From what i understand i had a cracked crankcase canister and external damage to the cats.

New cat, new canister, some random hoses and a fresh oil change.

Gave it a blast on the highway just to be sure.

Passed the mot with flying colors, the readings were perfect 0.13 % and 0.18 %.
So happy that it's all sorted.

Thanks guys for all the help.
Post Reply