exhaust emission warning light

UK forum for general and technical discussion about the Z3 roadster

Moderator: Gazza

Post Reply
andy & fonz
Joined: Tue 28 Jul, 2015 18:35
Posts: 44

  Z3 roadster 2.2i

exhaust emission warning light

Post by andy & fonz » Tue 08 Sep, 2015 12:36

hi everyone
got my 2.2 2001 z3 end of may this year, 58000 on the clock, am not sure this is true, the warning light was on when I got the car as I know the previouse owner I put this down to lack of use, he had spent the best part of £3000 with sytners 2000 miles ago on m.o.t and getting the light out, lambarda sensors changed, plugs , all breather pipes and filter, I have changed the rear pads the fittings had been bent to get them in the piston hence the rattle, also the cable for the locking fuel cap was broken fitted new one, offside bonnet catch broken new catch and both cables and handle renewed, have changed the air filter, fuel filter, engine oil and filter, put two tank fulls of fuel through with cleaners added, after resetting the warning light I have done 75miles with the light out it came back on after sitting in traffic, then I disconnected the maf with engine running it just died reconnected, filled up with shell v power, light stayed out for 100miles, now the pesky thing has come back on , the plugs are a good colour, only fault showing on my reader is emissions out of value, the tail pipe looks a bit black and it sounds as if its running rich, any ideas ? thanks for reading this ramble.
andy

User avatar
BladeRunner919
Joined: Fri 17 Feb, 2012 20:18
Posts: 2220

  Z3 roadster 1.9

Re: exhaust emission warning light

Post by BladeRunner919 » Tue 08 Sep, 2015 12:50

You need to get it on proper diagnostics rather than a generic code reader. Have a look at this thread to see if anyone with diags is near you:

http://www.zroadster.net/forum/viewtopi ... =5&t=36055

Hairyscreech
Joined: Thu 16 Apr, 2015 13:08
Posts: 69

  Z3 roadster 2.8

Re: exhaust emission warning light

Post by Hairyscreech » Tue 08 Sep, 2015 14:03

What Bladerunner said, sounds like it needs a proper diagnose instead of a generic reader shoved into it. I get the feeling it has a simple fault and the garages have been changing things to fix it without doing a proper diagnosis.

How well does it start when you turn the key?
What colour are your spark plugs?

Mike Fishwick
Joined: Fri 19 Jun, 2009 11:27
Posts: 1991

  Z3 roadster 2.8
Location: Daglan, France

Re: exhaust emission warning light

Post by Mike Fishwick » Tue 08 Sep, 2015 15:05

It is worth checking that the intake bellows pieces are both free from splits, as this will weaken the mixture and bring the emissions light on. It may not be this, but checking simple things first costs nothing.

Lots of BMW owners first go for an expensive diagnostic test, which brings up codes for 'Lambda voltage implausible' and after replacing both Lambda probes (people today seem to love replacing things, rather than thinking!) someone finds a split intake bellows!
A Z3 is not just for Christmas - it's for life!

Hairyscreech
Joined: Thu 16 Apr, 2015 13:08
Posts: 69

  Z3 roadster 2.8

Re: exhaust emission warning light

Post by Hairyscreech » Tue 08 Sep, 2015 15:30

As I have found while fitting the M50tu management onto the M20 in my E30, this generation of ECU chucks "implausible" or "Plausibility error" results for a whole range of unrelated reasons.
I have a plausibility error on one of the knock sensors at the moment which does not swap banks when I swap sensors bank to bank (there's only wire between them and the ECU, already checked that), I had both an "open circuit" and "short circuit" error on the TPS at the same time and the ECU does not seem to understand that the 328/M52 MAF plugged into it had the wrong resistance curve (M50 one was dead and I needed something to test with so threw it on).

They are not as clever as the manufacturers would like you to think and still need a lot of manual diagnosis, something garages just won't or can't do anymore.

Edit - It's also worth noting a plausibility error does not indicate a problem with the sensor at all, simply that the info/signal from it do not match the expected values based on the other information the ECU has.

andy & fonz
Joined: Tue 28 Jul, 2015 18:35
Posts: 44

  Z3 roadster 2.2i

Re: exhaust emission warning light

Post by andy & fonz » Tue 08 Sep, 2015 15:54

thanks for your replys guys, plugs are the right colour, starts first time tick over is spot on, m.pg 28.2 over 250 miles, all the bellows look to be o.k, have had the maf off and cleaned all the internals out and blown the flies out of the wire screen, wil go down the diagnostic route and let you know the outcome
andy

Hairyscreech
Joined: Thu 16 Apr, 2015 13:08
Posts: 69

  Z3 roadster 2.8

Re: exhaust emission warning light

Post by Hairyscreech » Tue 08 Sep, 2015 16:17

Worth bearing in mind there are some fault codes that will keep the light on until cleared out of the ECU, I think the ones that say "emission relevant fault" might be persistent and not self clearing.

andy & fonz
Joined: Tue 28 Jul, 2015 18:35
Posts: 44

  Z3 roadster 2.2i

Re: exhaust emission warning light

Post by andy & fonz » Tue 08 Sep, 2015 16:24

thanks, I keep clearing the fault every time I try something to fix the fault, I sometimes wonder if its my fault my other BM is a diesel and I find myself driving the z the same, perhaps I should keep filling it up with v power and drive it like I stole it !

therealdb1
Joined: Tue 25 Jun, 2013 22:47
Posts: 232

  Z3 roadster 2.0

Re: exhaust emission warning light

Post by therealdb1 » Wed 09 Sep, 2015 10:01

If it is running rich it may be that the ECU thinks the engine is cold.
Hook it up to an INPA and see what engine temperatures you are getting.
Also go to a friendly MOT station and get them to check the lambda and hydrocarbon readings at the exhaust. These will tell you if the mixture is over-rich rather than guestimating and it may save you having to buy a new cat too. However you would normally expect black spark plugs if the engine is over-fuelling.
You shouldn't need to drive a Z like a brainless lunatic just to keep the emissions within spec. That engine appeared in much more sedate saloons don't forget.
As Mike says emissions issues are more often than not split rubber somewhere and need nothing more than fingers and eyeballs to diagnose!
Don't forget to check the pipes that lead to the bellows as well.

User avatar
sirius-c
Joined: Wed 12 Dec, 2012 22:24
Posts: 489

  Z3 roadster 2.8
Location: Eeh ba gum lad, 'ow do?

Re: exhaust emission warning light

Post by sirius-c » Mon 21 Sep, 2015 22:21

therealdb1 wrote:If it is running rich it may be that the ECU thinks the engine is cold.
Hook it up to an INPA and see what engine temperatures you are getting.
I don't mean to hijack a thread but it seems like a good place to ask my question...
Mine's running rich, well, its trying too but the long term fuel trim is adjusting to Minus -11 to keep it in spec....
No black plugs, smoke, or sooty tail pipes, it ticks over and runs great, although the fumes from the exhaust smell a little on the rich side.
In an effort to reduce this LTFT I've done the following:-
I've had a terraclean, checked the fuel pressure regulator, checked fuel pressure with and without vac, also a leak down test to rule out a leaky injector (all are OK),
I replaced the one and only pre cat Titania lambda as it's switching frequency was approx 5 seconds between rich/lean...
now I'm running out of ideas and I can only assume its something to do with operating temperatures.

anyhow my question is.....
My running temp according to INPA is generally around 81-82 deg C, is this normal?
The temp gauge needle on the dash in bang in the middle

Note: 1997 2.8 auto with 60k on the clock
1997 2.8L Z3 Roadster

Image

Designed or not designed, that is the question.

Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2115

  Z3 roadster 1.9

Re: exhaust emission warning light

Post by Del » Mon 21 Sep, 2015 23:13

Is this LTFT problem (double-digit minus figure) across the rev range - if it is concentrated at low revs/idle it tends to point to a leaky injector - at higher revs this particular problem would tend to diminish. My Haynes manual states that the thermostat opening temperature for the 6-cylinder engine is 88 C - I am afraid that my expertise is not sufficient to know whether this would contribute to an overall temperature of around 81-82C at the point in the system where the temperature sensor takes its measurement

In my view the MAF sensor is likely to be the culprit causing "over-fuelling" if everything else is deemed to be running OK.

User avatar
sirius-c
Joined: Wed 12 Dec, 2012 22:24
Posts: 489

  Z3 roadster 2.8
Location: Eeh ba gum lad, 'ow do?

Re: exhaust emission warning light

Post by sirius-c » Tue 22 Sep, 2015 00:12

Hi Del, many thanks for your reply,

I'm sorry, I forgot to mention that i ruled the MAF out as part of my diagnosis, my original MAF was cleaned with residue free electric contact cleaner and I also purchased another MAF (2nd hand), both mafs run with almost identical voltage changes through different rev ranges so I'm assuming nothing is wrong. I've also checked and wiggled the MAF connector/wiring to rule out any problems there after reading a thread of someone experiencing the same problems as myself here:-
http://www.bimmerfest.com/forums/showpo ... tcount=141


I have only observed the STFT's and LTFT's whilst sat in the car at Idle and revving constantly at different ranges IE 1500, 2000, 2500
I've had this problem since I became aware of it in April. since then Ive reset adaptation values multiple times during my diagnosis attempts, then generally driven around for a couple of hundred miles before checking the LTFT's again.
Since LTFT's are exactly that, long term, I do this to allow the car to accumulate those LTFT values again, that said I do monitor the short term fuel trims at idle/low revs which are obviously trending negative until the LTFT is adjusted.
I should really reset the values again then have someone drive my car whilst I monitor the short terms with INPA and/or Testo to see whats happening under load too.
Testo is a fantastic app by the way, it allows real time graphing and CSV logging.
http://www.bimmerforums.com/forum/showt ... graph-view


It's interesting what you say about leaky injectors, Ive had the leak down test done which should theoretically rule that out, but, correct me if I'm wrong, the "Engine Roughness" part of INPA has been getting worse on 2 x cylinders...Although I'm not 100% sure exactly what this screen and its values are supposed to represent, I've convinced myself its something to do with either cylinder compression or misfires and that my worsening values may somehow be related to a couple of very minor leaking injectors.....but I ask myself how on earth is each cylinder monitored to provide this information to INPA? is there some kind of mystical sensor in each combustion chamber? I highly doubt it.

this diagnosis can go on and on, and believe me it has, its a real headache....if I'm to diagnose this based on my assumptions of the "Engine Roughness" it could be anything from a very minor leaky injector to coil packs to piston rings, but how so when the engine doesn't miss a beat? Idle is spot on and within spec, no hesitation or splutters on acceleration etc.
So...this is why I'm also considering the coolant temp side of things, maybe the wrong type of thermostat is installed and is opening at the wrong temperature or maybe a dodgy coolant sensor could be the culprit? I've no idea :rtm:

Sometimes I just think "Sod it", the fuel injection system is doing what its supposed to do anyway and is adjusting the values to keep them within spec, but I know that eventually when the LTFT's reach high enough negative values that they'll throw a permanent code and a CEL until I fix this elusive problem, and I'm pretty confident that the code thrown at me won't make me any wiser because it'll be a Lambda code and the Lambda's been replaced.
:bawl:
1997 2.8L Z3 Roadster

Image

Designed or not designed, that is the question.

Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2115

  Z3 roadster 1.9

Re: exhaust emission warning light

Post by Del » Tue 22 Sep, 2015 09:45

The only external thing I have read which can cause this sort of thing (and I’m not sure whether it is totally accurate) is where a higher octane fuel is used. The ECU would have been factory programmed for 95 octane (possibly even slightly less) and so if say, 98 octane is used, there may well be slightly more residual HC in the immediate combustion gas mix and so the lambda is asked to weaken the mixture slightly – hence people using highly octane fuel often report slightly higher MPG as it burns more efficiently.

As you say, it sounds as if the lambda is easily making the correction without throwing an error code to the ECU. So your fuel management system is operating within tolerance.

User avatar
sirius-c
Joined: Wed 12 Dec, 2012 22:24
Posts: 489

  Z3 roadster 2.8
Location: Eeh ba gum lad, 'ow do?

Re: exhaust emission warning light

Post by sirius-c » Tue 22 Sep, 2015 10:09

Del wrote:The only external thing I have read which can cause this sort of thing (and I’m not sure whether it is totally accurate) is where a higher octane fuel is used. The ECU would have been factory programmed for 95 octane (possibly even slightly less) and so if say, 98 octane is used, there may well be slightly more residual HC in the immediate combustion gas mix and so the lambda is asked to weaken the mixture slightly – hence people using highly octane fuel often report slightly higher MPG as it burns more efficiently.


I could believe that but the owners manual calls for super unleaded.
I even thought that the snake oils (Redex, STP etc) I've been religiously using might be causing it to run rich, but I stopped using them months ago.

I've pretty much reached a dead end regarding this problem now, I think my only option is to wait until something gives up the ghost as I refuse to throw parts at it.
1997 2.8L Z3 Roadster

Image

Designed or not designed, that is the question.

andy & fonz
Joined: Tue 28 Jul, 2015 18:35
Posts: 44

  Z3 roadster 2.2i

Re: exhaust emission warning light

Post by andy & fonz » Fri 25 Sep, 2015 16:19

hi
update, have removed all intake hoses and inspected they all seem to be ok, checked an old service invoice and found out they where all renewed 3000 miles ago, along with the sump to head hose and the cyclone filter.
took car to a idependant BM garage with the emission light on ,and guess what they told me the fuel trim levels were beyond spec, could be a oxygen sensor fault, has these were only renewed with genuine BMW parts again 3000 miles ago I can not believe they are done for already.
the error codes have been cleared again and when the light comes back on I shall return for another check, in the meantime have filled up with v power fuel to see if this makes a differance

andy & fonz
Joined: Tue 28 Jul, 2015 18:35
Posts: 44

  Z3 roadster 2.2i

Re: exhaust emission warning light

Post by andy & fonz » Sat 31 Oct, 2015 19:05

hi
have been running on shell v power and the warning light has stayed out, 300 miles or so,lets hope it stays that way

peter2b
Joined: Sat 01 Nov, 2014 18:47
Posts: 933

  Z3 roadster 2.2i
Location: cheshire

Re: exhaust emission warning light

Post by peter2b » Mon 02 Nov, 2015 20:49

Mike Fishwick wrote:It is worth checking that the intake bellows pieces are both free from splits, as this will weaken the mixture and bring the emissions light on. It may not be this, but checking simple things first costs nothing.

Lots of BMW owners first go for an expensive diagnostic test, which brings up codes for 'Lambda voltage implausible' and after replacing both Lambda probes (people today seem to love replacing things, rather than thinking!) someone finds a split intake bellows!
I had the same on my Z3 2.2 split intake hose was the cause
peter2b

Post Reply

Who is online

Users browsing this forum: No registered users and 4 guests