MOT Emmission failure/pass

UK forum for general and technical discussion about the Z3 roadster
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Parki
Joined: Sun 02 Feb, 2014 17:42
Posts: 91

  Z3 roadster 1.9

MOT Emmission failure/pass

Post by Parki »

Help - I took my 1.9 '97 for MOT on Monday & it failed due to emmissions too high -

Fast Idle test - CO failed at 6.546! (max 0.3) HC passed 180 (200max) Lambda read 0.826 marked as fail although max limit is 1.03(?).
2nd fast idle test - CO failed at 5.721! HC passed at 177 & Lambda failed at 0.848
Natural idle test CO read 3.776! (max 0.5)

I then asked about proper warm up as mentioned on this site & Z was re tested using a fuel additive & getting really warm - result pass -

Fast Idle test CO now 0.004! HC 0 ! Lambda 1.005
2nd fast idle Not Done(?)
Natural Idle CO again 0.004

Besides the difference in figures seeming crazy to me - I'm left feeling there is some problem with cold running management. On a 20 mile run mpg starts at 27.5 but after 20 mins begins to rise & at 40 mins shows 34 & hits 38 on longer runs. I think diagnostic is called for but am 3 hrs away from nearest member with diagnostics & am unimpressed with garage diagnostics so could it be worth investing in equipment myself although find read ups confusing?

Any comments appreciated
Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2136

  Z3 roadster 1.9

Re: MOT Emmission failure/pass

Post by Del »

Huge difference in CO which suggests it was running very rich on the first tests - did they bother to warm the car up properly? A faulty thermostat (commonly they stick open) might cause the engine to run a little richer for longer but your results are dramatic. It is appreciated in the trade that certain BMW cats can take a longer time to get up to operating temperature - again that could contribute to this difference. :shrug
Parki
Joined: Sun 02 Feb, 2014 17:42
Posts: 91

  Z3 roadster 1.9

Re: MOT Emmission failure/pass

Post by Parki »

Hi Del - tester said it was warm at first test but I was not present - obviously it was warm enough 2nd time. Thermostat replaced recently when temp guage failed to get to 12 o clock position as it does now within about 5/10 mins. Have also replaced Engine temp & exhaust sensers some months ago.
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Robert T
Site Admin
Joined: Mon 12 Jun, 2006 10:35
Posts: 10170

  Z3 roadster 1.9
Location: Cheshire

Re: MOT Emmission failure/pass

Post by Robert T »

Looks like they still had the probe shoved up the exhaust of the VW diesel parked next to it! :evil:

I suspect that catalytic convertors get less efficient with time and so take longer to get up to operating temperature whereby they can do their stuff. Not sure what else would cause it to run rich at startup, but you might check the intake bellows for leaks.

Cheers R.
Arctic Silver '99 Z3 1.9 & Black '59 Frogeye 1275cc
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therealdb1
Joined: Tue 25 Jun, 2013 21:47
Posts: 263

  Z3 roadster 2.0

Re: MOT Emmission failure/pass

Post by therealdb1 »

Lambda has a lower limit too of 0.97 which is why your car failed on it first time round.
In my experience of MOT tests you are very much at the mercy of the tester and his ability to interpret the instructions for the test and what the results are telling him.
For example, the tester is supposed to measure the oil temperature to confirm that the engine is at operating temperature. The Government issues a list of approved oil temperature measurement devices for MOT's and the instrument is to be regularly calibrated. Ever since the inception of the emissions test, probably around the early 1990's when cars had to have a cat fitted, I have never seen any tester measure the oil temperature.
In fact I had an MOT on my daily driver yesterday and it clearly states on the emissions readout that the oil temperature measurement was bypassed! Checking the water temperature gauge on the dashboard does not confirm that anything other than the water in contact with the sensor is at that temperature and the rest of the engine, sensors and exhaust could still be comparatively cool and not functioning as BMW intended allowing the emissions to be outside the limit as you found.
At least you got a second chance and passed once the car was warmed up. When my daily use Volvo was 2 years 11 months old I took it to a local garage for its first ever MOT. Suprisingly it failed on emissions. I called the nearest franchised dealer, 40 miles away, and they said that cars like mine never fail MOT's on emissions and if I took the car to them they would check it using their equipment. After an 80 mile round trip I had an emissions printout which showed the car was spot on as it should have been with 20,000 miles on the clock from new. I took the sheet back to the garage that had failed my car the day previously only for the mechanic to apologise and say that their emissions equipment was faulty and he thought it strange that every car he tested that day, about 15 cars from memory, had failed on emissions! :head:
Our mechanic friends are not always the sharpest tools in the box!
Parki
Joined: Sun 02 Feb, 2014 17:42
Posts: 91

  Z3 roadster 1.9

Re: MOT Emmission failure/pass

Post by Parki »

Thanks for responses - will check hoses/bellows for leaks & yes Eng oil temp was by passed so its likely it was not 'hot' when failed.
But mpg IS poorish & I know we dont drive zeds for economy but don't like the feeling somethings not right so a diagnostic check seems to be the next step - would a bunged up cat show on read out (other than O2 sensor problem)? How much does a good diagnostic kit cost & how easy to use? Trying to follow previous threads on diagnosing I got lost very early?
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colb
Joined: Sat 05 May, 2012 22:46
Posts: 690

  Z3 roadster 1.8 TU
Location: Newport South Wales UK

Re: MOT Emmission failure/pass

Post by colb »

Diagnostics kit here
http://www.ebay.co.uk/itm/BMW-USB-OBD-D ... 1128248013

Need a good Laptop with loads of disc space for this and practice in using it.

A simple code reader that you can use in iPhone or ipad is an alternative also available on ebay WiFi (ELM327 Interface) but you also need the round diagnostic plug and cable to 16pin OBDII socket and an App such as Dash Command on the phone or ipad.

http://www.ebay.co.uk/itm/ELM327-WiFi-O ... SwkNZUfq9U

http://www.palmerperformance.com/products/dashcommand/

Either will give you access to codes and the ability to clear them.

For Airbag codes and resetting you need a completely different code reader but again available on ebay
http://www.ebay.co.uk/itm/Airbag-Reset- ... SwVL1V~o6x

Always use the under bonnet round socket to connect to, if you have the 16pin OBDII socket under the steering wheel that will only read certain engine codes.

If you go the BMW Cables route plenty of threads on here to assist with loading it and getting it running
Colb
1999 BMW 1.8 Z3
2003 BMW 2.5 Z4
1998 Honda Deauville NT650V
therealdb1
Joined: Tue 25 Jun, 2013 21:47
Posts: 263

  Z3 roadster 2.0

Re: MOT Emmission failure/pass

Post by therealdb1 »

If you intend keeping the car and intend working on it yourself, or at least like to have an idea what is wrong with it before you take it to someone else to fix, plump for an INPA set up like colb's first suggestion.
It does so much more than read codes eg. you can look at sensor outputs in real time (with someone else driving of course! :) ), you can set adaptions for things like the throttle although I don't think you need this function on your car, and as long as you get the version where the screen is in English rather than German (check with the seller before you buy it) you get a much more descriptive indication of what the fault is rather than some hexadecimal number or a generic code that you have to search through tables for and then find that you are none the wiser.
I would also say that you do not need some hyper-powerful laptop either. I first used it perfectly adequately on an 8 year old laptop running Windows XP although I subsequently upgraded as the laptop battery died and it had to be mains powered.

However looking at the results of the second test your emissions look fine. My car is a 2 litre 6 pot but gave 0.008 CO, 30ppm HC and 1.01 lambda at its last test so it is worse than yours!

I think you may be expecting a bit much if you think mpg of between 27 and 38 is poor. What are you comparing it to? Remember it will be 20 years old next year and you do not state its mileage. My handbook gives fuel consumption for a 4 pot as 26 mpg urban cycle and 36 all around driving and that is obviously when the car was new and probably includes optimistic adjustments for weather and traffic conditions. I have never managed to achieve manufacturer's figures for any car that I have owned; the nearest I ever got was 14 mpg on a supercharged 4 litre Jaguar for which they quoted 17 mpg but then it had so much torque you could drive everywhere at tickover :D If you wanted to match the 0-60 time of 5.7 seconds the trip computer said 4 mpg and you bought shares in an oil company at the earliest opportunity!
Parki
Joined: Sun 02 Feb, 2014 17:42
Posts: 91

  Z3 roadster 1.9

Re: MOT Emmission failure/pass

Post by Parki »

Again, thanks for in puts. I've got plenty of things to check & it makes sense to go down self diagnostic route. As I was trying to say before, it is not a nissan micra & if the car is happy then so am I - just need to prove to myself it is. Again thanks for all the help, lots to ponder on.
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