1997 Z3 Emissions Problem - any suggestions ?

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chrisgoodwin
Joined: Sun 12 Jul, 2015 18:10
Posts: 6

  Z3 roadster 2.8

1997 Z3 Emissions Problem - any suggestions ?

Post by chrisgoodwin »

Hi
I have a 1997 2.8 Z3. It failed its MOT last week on emissions - all readings were well over acceptable limits apparently. I have only had the car for a year so this is the first time I have taken it for MOT; however, looking back it has had this problem every year since 2004.
I had it Terracleaned, made sure it had a good run before it went for re-test and it has still failed badly.
The garage said they don't think its the CAT or sensors and suggest basically pulling the car apart and replacing everything until the readings are within limits - engine rebuilds were mentioned. I have a bill for engine work carried out two years ago and a new CAT was fitted at the same time. I have had someone drive behind me and there is no smoke - I realise that this is does not mean the emissions levels are ok, but would have expected something if it was so bad the engine needs rebuilding; it also pulls like a train and doesn't overheat.
There were no other advisories and since its Terraclean it drives even better than before.
I feel I could scream, I don't want to scrap an otherwise good car, but as I also had a new clutch fitted last week wonder if its worth it.
Any help or suggestions would be very welcome.
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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: 1997 Z3 Emissions Problem - any suggestions ?

Post by colb »

Have you checked to see if it has set any codes which might point to dodgy sensors causing misfueling and bad emissions?

My guess would be Maf, and or exhaust sensors or cat contributing to bad emissions.

What mileage has it done?
Colb
1999 BMW 1.8 Z3
2003 BMW 2.5 Z4
1998 Honda Deauville NT650V
chrisgoodwin
Joined: Sun 12 Jul, 2015 18:10
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  Z3 roadster 2.8

Re: 1997 Z3 Emissions Problem - any suggestions ?

Post by chrisgoodwin »

Hi
It has done 101917 but most of that was done early on in its life for the last few years it has only done 2 or 3000 per year. From the paperwork I have, of which there is a lot although not totally complete, it has been well maintained.
I have now booked it into a local specialist to see what they think. I only have a basic code reader and I'm not at all sure it reads it properly.
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colb
Joined: Sat 05 May, 2012 22:46
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  Z3 roadster 1.8 TU
Location: Newport South Wales UK

Re: 1997 Z3 Emissions Problem - any suggestions ?

Post by colb »

OK the high mileage would lead me in the direction of worn valve guides but you say no smoke when you have been followed, if it is valve guides you are more likely to see smoke on the over run when decelerating as oil would be passed by the valve stems and burnt in the cylinders. What colour are the spark plugs, any oil on them are they black or a nice biscuit brown?
Colb
1999 BMW 1.8 Z3
2003 BMW 2.5 Z4
1998 Honda Deauville NT650V
chrisgoodwin
Joined: Sun 12 Jul, 2015 18:10
Posts: 6

  Z3 roadster 2.8

Re: 1997 Z3 Emissions Problem - any suggestions ?

Post by chrisgoodwin »

It runs nice and clean and the plugs are a nice shade of brown, with no oilyness at all - had them out and had a good look when it failed the first time. I did get the compression checked a while ago and that was all fine too. Just hoping its not going to result in another large bill.
Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2136

  Z3 roadster 1.9

Re: 1997 Z3 Emissions Problem - any suggestions ?

Post by Del »

What are the exact MOT emission problems? Is it just high CO?
chrisgoodwin
Joined: Sun 12 Jul, 2015 18:10
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  Z3 roadster 2.8

Re: 1997 Z3 Emissions Problem - any suggestions ?

Post by chrisgoodwin »

Everything was wrong apparently - I did not get a print out with the exact percentages -
carbon monoxide content at idle excessive
" " " after second fast idle excessive
hydrocarbon content after second fast idle excessive
lambda reading after second fast idle outside specified limits
Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2136

  Z3 roadster 1.9

Re: 1997 Z3 Emissions Problem - any suggestions ?

Post by Del »

These problems indicate a rich combustion mixture (CO), incomplete combustion burn (HC) and too much oxygen content in the exhaust gas (Lambda) – a high lambda reading at the exhaust is not necessarily linked to a fault with the exhaust sensor with the same “lambda” name i.e. the lambda sensor – this is a common mistake/misconception. For example, a high exhaust gas lambda reading IN ISOLATION is commonly associated with an exhaust leak and air being sucked in. the fact that you have a problem with all three could indicate lots or separate problems or (in my opinion) a single problems causing all three.

Assuming your plugs, air filter and ignition coils are all operating properly I would definitely start with plugging the car into a code reader. Your car, like mine, is pre-OBD compliant and therefore does not have an error light on the dash which lights up if an engine management sensor is faulty. A simple OBD II code reader works on my car with a conversion cable to plug into the round socket under the bonnet. I’ve seen unnoticeable faults with the camshaft position sensor (controls ignition timing) cause poor exhaust readings.

Personally, I don’t think that 100,000 miles on a cared for 2.8 is high mileage – these engines are bullet-proof and easily capable of 200,000+ miles. As one old BMW technician said to me, these older 6-pot engines are virtually indestructible and can cope with a certain amount of “servicing abuse”. Given your compression is good (and assuming you aren’t burning oil) I would be amazed if the engine needed some sort of rebuild.

Start with the code reading.
chrisgoodwin
Joined: Sun 12 Jul, 2015 18:10
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  Z3 roadster 2.8

Re: 1997 Z3 Emissions Problem - any suggestions ?

Post by chrisgoodwin »

Many thanks that sounds a little more hopeful :)
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lightning
Joined: Tue 27 Nov, 2007 08:15
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  Z3 roadster 3.0i
Location: Stockport

Re: 1997 Z3 Emissions Problem - any suggestions ?

Post by lightning »

When you said you took the car for a good run, did you give the engine a decent workout? As in some high engine RPM and full power acceleration?
My friend had a Toyota Celica that failed emissions, even though he'd taken it for a drive beforehand. Taking advice from the testing garage he took it out again and gave it a good drubbing, after which it passed.
bertiejaffa
Joined: Fri 26 Jul, 2013 09:28
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  M roadster S50
Location: Manchester

Re: 1997 Z3 Emissions Problem - any suggestions ?

Post by bertiejaffa »

As said, 100K miles is not high for a car, if that was the case all 4 of mine would fail their MOT. I am also suspicious when you said they didnt give you the sheet with the readings on - they should have done - it is yours ! I'm even more suspicious when they talk about engine rebuilds ?!?!?!?

As Lightning says... a good run out is not the same as "a good run out". Assuming your old MOT hasn't run out yet find a good 30 mile country route and drive it like you stole it. The smile on your face will still be beaming when you drive off with your new MOT certificate.
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Alan W
Joined: Thu 20 Jun, 2013 10:56
Posts: 670

  Z3 roadster 2.8
Location: Bexley, Kent UK

Re: 1997 Z3 Emissions Problem - any suggestions ?

Post by Alan W »

Hi Chris,

May be worth trying Dipetane..

Add it at a higher mix (it won't hurt the car) and then take it for a very spirited drive for a good few miles...

I get this from the independent car spares shop where my brother works and I regularly put it in my car. I have posted about it in the past and some suggested that it was 'snake-oil'.. however, the fact is that a lot of my brothers customers are small independent garages and many use it to get cars with high emissions through their MOT and they swear by it.. and this is what they do.. put it in the fuel tank and give the car some welly for a few miles then straight to the testing station.. (I don't like the sound of the one you went to so try another)..

The manufacturer makes all sorts of interesting claims about it and some 'clean' fuels have Dipetane added..

However, there is clearly something wrong with your emissions which needs to be fixed... but Dipetane could get it through the MOT enabling you to still carry on driving your car leaving you to carry out a process of elimination at your leisure..

I have no allegiance to the product and have not noticed any increase in MPG.. my car has never failed on emissions before or since using it.. and I use it solely because (a) I believe that it keeps my fuel lines, injectors and engine clean, and (b) I get it at a discount price via my brother

Hope you manage to get it all sorted mate
1999 facelit Z3 Roadster 2.8 Auto in Cosmos Black aka 'Gloria'
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Robert T
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  Z3 roadster 1.9
Location: Cheshire

Re: 1997 Z3 Emissions Problem - any suggestions ?

Post by Robert T »

There are many reasons why the car could fail on emissions, and it is going to be a case of working through them all. However, number one reported on here is the car (and CAT) not being up to temperature when tested - you can take it for a good run beforehand, but if it sits on the forecourt for hours before they test it, then it will have been for nothing.

In addition to those things already mentioned, check for a split in the bellows between the MAF and the inlet manifold. This lets unmetered air into the system and confuses the ECU as to how much fuel to put in.

Cheers R.
Arctic Silver '99 Z3 1.9 & Black '59 Frogeye 1275cc
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gookah
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  Z3 roadster 2.8

Re: 1997 Z3 Emissions Problem - any suggestions ?

Post by gookah »

Mine failed once on emissions lambda too high. This was down to a spilt in the air intake hoses after the MAF
Check these first as they are a regular problem at this age and they are only about £13 each from BMW.
They can cause overfueling also
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chrisgoodwin
Joined: Sun 12 Jul, 2015 18:10
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  Z3 roadster 2.8

Re: 1997 Z3 Emissions Problem - any suggestions ?

Post by chrisgoodwin »

Thank you all for your replies; I will go and check the hoses as soon as it stops raining for long enough !
When it went for the first test I dropped the car off in the morning and it did sit for a couple of hours before it was tested.
When I took it for the re-test I made sure it had a good run of 10-15 miles of dual carriageway and quiet lanes - so it was fully up to temp and driven in a "spirited" manner
I have used the mot station for quiet a few years and they have always been very fair, although they have recently got a lot bigger and taken on more staff. I do sometimes wonder if some garages try to do unnecessary work as I am female and they think I don't know any better,I had this experience recently when buying tyres - when I arrived they tried to tell me I was fitting the wrong ones and needed different tyres at £150 more however when my husband came in they changed their tune and decided I was right after all. I would be surprised if that were the case here though as I assume they would have to show me the readings if I insisted.
bertiejaffa
Joined: Fri 26 Jul, 2013 09:28
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  M roadster S50
Location: Manchester

Re: 1997 Z3 Emissions Problem - any suggestions ?

Post by bertiejaffa »

chrisgoodwin wrote:Thank you all for your replies; I will go and check the hoses as soon as it stops raining for long enough !
When it went for the first test I dropped the car off in the morning and it did sit for a couple of hours before it was tested.
When I took it for the re-test I made sure it had a good run of 10-15 miles of dual carriageway and quiet lanes - so it was fully up to temp and driven in a "spirited" manner
I have used the mot station for quiet a few years and they have always been very fair, although they have recently got a lot bigger and taken on more staff. I do sometimes wonder if some garages try to do unnecessary work as I am female and they think I don't know any better,I had this experience recently when buying tyres - when I arrived they tried to tell me I was fitting the wrong ones and needed different tyres at £150 more however when my husband came in they changed their tune and decided I was right after all. I would be surprised if that were the case here though as I assume they would have to show me the readings if I insisted.
Make sure you get the readings and NEVER do anything before asking on here - theres more info on here then any BMW garage... at the end of the day the maybe correct but this place will verify it for you. There are also people who will help you do it in some instances.
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