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Discussion Starter · #1 ·
Hi there,
I have just had an MOT failure on a 1994 ///M3 3.0 on high CO emissions and am just looking for some advice on solving the problem please.
It was quite far out and running rich at 0.7 %wt CO rather than the permissable 0.2. Lambda readings were acceptable.
The car has had an inspection 2 service at 111,500 miles (now 114,500m) and that was in late May 2008. The guy at the MOT station said that it may just be due a service and that would improve the emissions. Is this the case, even although it was less than a year and 3,000 miles ago?!
I have had a look at the usual faults and have got some contact cleaner to give the air flow meter a clean, I'll clean the air filter too (K&N cone - I may switch back to the original airbox if this will help matters?!)
Could the throttle position sensor require replacing?
Am I likely to see any benefit from replacing the plugs and oil etc etc?
I also have a performance chip and thought that the improved state of tune may help reduce the emissions? Or should I stick with stock chip until after the MOT?

Any advice would be much appreciated :)
Cheers!
Al
 

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Hi there,
I have just had an MOT failure on a 1994 ///M3 3.0 on high CO emissions and am just looking for some advice on solving the problem please.
It was quite far out and running rich at 0.7 %wt CO rather than the permissable 0.2. Lambda readings were acceptable.
The car has had an inspection 2 service at 111,500 miles (now 114,500m) and that was in late May 2008. The guy at the MOT station said that it may just be due a service and that would improve the emissions. Is this the case, even although it was less than a year and 3,000 miles ago?!
I have had a look at the usual faults and have got some contact cleaner to give the air flow meter a clean, I'll clean the air filter too (K&N cone - I may switch back to the original airbox if this will help matters?!)
Could the throttle position sensor require replacing?
Am I likely to see any benefit from replacing the plugs and oil etc etc?
I also have a performance chip and thought that the improved state of tune may help reduce the emissions? Or should I stick with stock chip until after the MOT?

Any advice would be much appreciated :)
Cheers!
Al

What's the milage on your car mate?
 

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As suggested by Ray, you first need to check for air leaks. I can get photo's of the pipes you need to check as my car has the inlet manifold off and I've been meaning to do for a while now:thumbsup

There are a lot of air pipes that could be the cause:frown
 

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Discussion Starter · #7 ·
I'm assuming its the pipes around the ICV, AFM and the inlets to the throttle bodies? Ive checked the rubber covers on the top of the throttle bodies and they're all intact. Ive stripped the M3 engine down on a friend's car before so no job is too hard, if it'll fix the high CO readings!

From the MOT:
Fast Idle test: CO - 0.79 %vol (0.97 %vol 2nd test) (0.3 %vol is the limit)
HC - 214ppm (212ppm 2nd test) (200ppm is the limit)
Lambda - 1.03 (1.02 2nd test) (1.03 is the limit)
Natural Idle: CO - 0.79 %vol (0.5%vol is the limit)

So it's pretty far out for the CO isnt it? HC levels were below 200ppm on the unofficial test he did before the MOT...
Best start dismantling the car now then!
Cheers for the advice so far guys, its much appreciated :)
 

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Discussion Starter · #8 ·
Re: O2 Sensors: there is nothing in the service history about them being replaced and there are no receipts for new ones so I'm afraid I don't know how old they are :-(
They wont be cheap to replace i'd imagine though?!
Cheers,
Al
 

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Re: O2 Sensors: there is nothing in the service history about them being replaced and there are no receipts for new ones so I'm afraid I don't know how old they are :-(
They wont be cheap to replace i'd imagine though?!
Cheers,
Al

O2 sensors for the 3.0 ar around £55 each for Bosch units.

Looking at the emisions, I personally would go with a dodgey cat.

Air leaks would cause over fueling- high HC
Your Lambda readings are on the limit but a pass.

A replacement after market cat can be bought for around £235. Be warned though, these are crap. They do the job but sound tinny and sit lower, which can be a real headache!! They also use smaller mickey mouse cats, which strangle some power.......I know, I bought one!!
OEM ones cost 3 times that. I run my M3 de-catted and swap the cat over for the MOT- so not fussed.

If your gonna keep the cat on full-time, then I would recommend you get hold of a good 2nd hand one- they go for around 150.

Also if the O2 sensors have not been changed, at that milage, they need replacing anyway, whether you get a new cat or not. You could try replacing the O2's and see how that effects the emisions.



Ronnie is the expert on these figure's...........he'll be around late this evening.........when he stumbles home from the local.
 

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Discussion Starter · #10 ·
hehe, I'll look forward to his reply :)

Cheers for that info - although, sadly, this is looking like a more and more expensive fix as time goes on!

The last owner mentioned that he thought that it had racing cats but he wasnt sure. Is there any obvious way that I could determine whether this is true or not? A de-cat would be my favoured option but as you say, it has to be changed for the MOT. I dont mind doing this but do you think it would be wise to buy a non-OE cat to get thru the MOT and then de-cat it, or do you think its a bit risky using the sub-standard cat at all, even for a short time period?!
Cheers mate:)
 

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Discussion Starter · #12 ·

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hehe, I'll look forward to his reply :)

Cheers for that info - although, sadly, this is looking like a more and more expensive fix as time goes on!

The last owner mentioned that he thought that it had racing cats but he wasnt sure. Is there any obvious way that I could determine whether this is true or not? A de-cat would be my favoured option but as you say, it has to be changed for the MOT. I dont mind doing this but do you think it would be wise to buy a non-OE cat to get thru the MOT and then de-cat it, or do you think its a bit risky using the sub-standard cat at all, even for a short time period?!
Cheers mate:)

Racing cats???

What I would do is get under the car and take a buthers at the cats. See exactly what you've got on there first.

If you are gonna be running decats then I would go with the cheaper replacement cats- that is what I do.

Try Cats and Carbs on tel: 01782 392202.

I got my M3 3.0 Cat for 235 all in. but if you can get a good decent 2nd hand one, then go for that- should be around 150 ish.

try quarry motors, etc.
 

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Here is a link to a cheap cat, what do you think? http://cgi.ebay.co.uk/BMW-M3-3-0i-7...14&_trkparms=72:1683|66:2|65:12|39:1|240:1318

Also found this full system from XS power but it looks like there is simply one front silencer rather than two cats, I assume this is bad?!:

http://cgi.ebay.co.uk/BMW-E36-M3-92...14&_trkparms=72:1689|66:2|65:12|39:1|240:1318

What do you reckon?
Cheers


XS- power!!!!!!

...........heard bad things about these guy's, they sell cheap crap from what I heard.
They used to sell (don't know if they still do) turbo conversions for the beemers.......a few customers had bought them, found they were crap, manifolds used to crack and did not fit as they were for bloody left hookers.
 

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Discussion Starter · #15 ·
Ok I'll give Cats & Carbs a call.

Are we all in agreeance that the MOT guy's advice of an oil change, plug change, general service etc won't help my emissions problem?

I'll get some new cats and a couple of lambda sensors.
Ive seen the lambda sensors advertised as pre cat L & R and post cat.
Havent had a good look but I'm assuming the only difference in the L & R will be cable lengths and its the 4 wire ones I want, yes?
Didnt know the M3 had a post-cat lambda sensor too?!
Cheers :)
 

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Ok I'll give Cats & Carbs a call.

Are we all in agreeance that the MOT guy's advice of an oil change, plug change, general service etc won't help my emissions problem?

I'll get some new cats and a couple of lambda sensors.
Ive seen the lambda sensors advertised as pre cat L & R and post cat.
Havent had a good look but I'm assuming the only difference in the L & R will be cable lengths and its the 4 wire ones I want, yes?
Didnt know the M3 had a post-cat lambda sensor too?!
Cheers :)


Hang on dude,

The 3.0 dos not have post O2 sensors, there are only the 2 pre-cat sensors.
 

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I know this may sound a little silly, but my husbands got a 3.0 e36 m3, done 160k. We had the same problem on the MOT last yr, we changed the lamda sensor, cats etc and still no improvement.
Then the car broke down, and we had to change the fuel pump, not a cheap thing really, but after we replaced that the car was fine on emissions.
 

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From the MOT:
Fast Idle test: CO - 0.79 %vol (0.97 %vol 2nd test) (0.3 %vol is the limit)
HC - 214ppm (212ppm 2nd test) (200ppm is the limit)
Lambda - 1.03 (1.02 2nd test) (1.03 is the limit)
Natural Idle: CO - 0.79 %vol (0.5%vol is the limit)

So it's pretty far out for the CO isnt it? HC levels were below 200ppm on the unofficial test he did before the MOT...
Best start dismantling the car now then!
Cheers for the advice so far guys, its much appreciated :)
Looks like a air leak :thumbsup

HC is unburnt fuel. is high on your car really IMO.

And as mentioned in post above fuel pressure will effect emissions, but I wouldn't get that far in yet.

Check for air leaks from split pipes e.t.c
 

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Discussion Starter · #20 ·
Cool, I'm getting stuck into removing the airbox etc tonight so I'm praying I find a split hose somewhere that I can just replace quickly and cheaply!
Cheers everyone. Will let you know if I find anything.
 
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