Cats / Emissions 3.0si Coupe

C

coupedan

Member
 West Berkshire
Just had my MOT which passed with no advisories :driving:

However, the tester noticed that my emissions on the "Fast-Idle" check were struggling to get under the Max threshold of 1.030ppm mine was at 1.027ppm. He said he had to test it 3 times to get it under as the first 2 were over the max.

So my questions are.. Has anyone had any experience with the cats failing on a 3.0si?
Is it likely to be first or secondary cats?
Could it be the lambda sensors are failing?

If it is the cats.. are there any performance gains to be had by installing sport cats, if they are available?

Car info..
It gets run on Shell V-Power Nitro+ with a fresh tank at least once a week.
Gets driven daily fairly hard - After all it is a sports car.
Before my MOT - I gave it the good old fashioned "Italian tune-up" to heat up the cats.
Car is a 2006 Coupe with just under 115k miles on the clock.

Any advice will be welcome :thumbsup:
Dan.
 
I don't think it'd be to do with the secondary cats as our engine can pass it's MOT with them removed (as long as they look like they're there visually!)
 
RyanB88 said:
I don't think it'd be to do with the secondary cats as our engine can pass it's MOT with them removed (as long as they look like they're there visually!)
Click to expand...

Ahh.. this was my worry as I know the primary cats are in the manifold - could be potentially costly me thinks!
 
coupedan said:
RyanB88 said:
I don't think it'd be to do with the secondary cats as our engine can pass it's MOT with them removed (as long as they look like they're there visually!)
Click to expand...

Ahh.. this was my worry as I know the primary cats are in the manifold - could be potentially costly me thinks!
Click to expand...


I wouldn't worry about it yet, you should have at least 12 months ! You may find if you take it to another garage next year they might find their systems don't have the same troubles with getting the emissions right!
 
This is true.. although I would much rather sort it ASAP rather than get round to MOT time next year and be hit with a £5k bill...
 
I wonder if it says more about the tester's equipment than your car - which is a lovely choice of Z4 by the way!

Mine had an amber EML light come on last year which my BMW indy said was due to a cat fault. He cleared it and I made sure I only used it for spirited, longer distance drives and it's been OK since - thankfully!

It hadn't long passed an MOT so I asked why it would have passed that and he told me the threshold on the OBD set-up is set at a more stringent level than the MOT requires. He also said new cats would be in the £2K bracket, so I wouldn't rush to replace them as a preventative measure! :roll:
 
Mr Tidy said:
I wonder if it says more about the tester's equipment than your car - which is a lovely choice of Z4 by the way!

Mine had an amber EML light come on last year which my BMW indy said was due to a cat fault. He cleared it and I made sure I only used it for spirited, longer distance drives and it's been OK since - thankfully!

It hadn't long passed an MOT so I asked why it would have passed that and he told me the threshold on the OBD set-up is set at a more stringent level than the MOT requires. He also said new cats would be in the £2K bracket, so I wouldn't rush to replace them as a preventative measure! :roll:
Click to expand...

Thanks :thumbsup:
But could be the testers equipment to be fair.. it easily flew through last year but it has also been smelling ever so slightly "Catty" (not the egg smell but the metallic burning type smell) that you get once a cat is on its way out.. so does beg the question.. are the cats on their way out.?

It's good to know that the OBD values are more stringent than what an MOT would test, plus I have had no engine warning lights so it should be fine.

If only there is a way to go fully decat and still be legal! ;)
 
I am always very sceptical on emission testing equipment. I had a Porsche 996 C4S which failed the emissions test at Halfords. They suggested I take it to a Bosch garage to check which sensors were faulty or not working. I did this and was told absolutely no problem with the sensors which if there were would show up once the car was plugged in to a diagnostic machine. Bill was £55 for an mot compared with around £500 to replace sensors that were working fine. It seems a lot of garages have faulty equipment which give a lot of headaches to us car owners. Reported the garage to the MOT inspectors but heard nothing
 
If it were me I would take it another garage and get them to test the emissions. At least that way you'll know if you have a genuine problem or not. Then go from there in terms of hunting down the problem. If it does turn out to be the Cats then at circa £2k I would be looking at used parts, its not like the Cats are known to fail so used replacements will hopefully be ok and no where near as pricey as new. Alternatively I would go down the route of seeing if any exhaust specialists can piece in new cats to the manifold, even if it means having them removed locally and couriered to the exhaust specialist.
 
RyanB88 said:
I don't think it'd be to do with the secondary cats as our engine can pass it's MOT with them removed (as long as they look like they're there visually!)
Click to expand...

Has anyone been able to verify this?
 
I've seen it said in that thread before, but was wondering if anyone had actually passed an MOT without these two underfloor cats.
 
coupedan said:
RyanB88 said:
I don't think it'd be to do with the secondary cats as our engine can pass it's MOT with them removed (as long as they look like they're there visually!)
Click to expand...

Ahh.. this was my worry as I know the primary cats are in the manifold - could be potentially costly me thinks!
Click to expand...


Hi, with the mileage on your car this could easily be a sign of a failing ccv system.
Are you burning oil/have sooty tail pipes?
Rob
 
HI coupedan.
Good to hear your car passed its MOT though.
Regarding the near threshold Lambda reading.

If you genuinely want to find out why the reading was close. and not speculate, find a garage who is conversant with the live data given from the O2 sensors, pre and post CAT. Also with short and long term fuel trims.

Shouldn't be too difficult to assess the performance of the various sensors.

i do an oxygen storage test, that involves sending the mixture rich and looking at how fast the o2 sensors react with an oscilloscope.

More accurately, how long it takes the post CAT sensor to drop lean when the rich mixture is removed, and compare it to the pre CAT sensor. This will accurately determine if any CAT is struggling.

Not cheap, but conclusive.

Alternatively, get a bottle of CATACLEAN and follow the instructions on it. Cost is about £15 and well worth it. Trust me on this.
If you don't believe me, or are skeptical, type in cataclean reviews and prepare to be amazed.

Additionally, make sure the oil and filter are changed regularly and as stated above, any crankcase ventilation systems are clean and clear.

Any slight exhaust leaks will also affect the lambda readings.

Hope all this helps!
An alternative to all this is to enjoy the car and worry about it next year!!

Andy.
 
Bluecat - I am always very sceptical on emission testing equipment. I had a Porsche 996 C4S which failed the emissions test at Halfords. They suggested I take it to a Bosch garage to check which sensors were faulty or not working.
Click to expand...

You raise a good point.. maybe I'll go and get it tested again in a few months to see if another garage gives different readings.

Mr Tidy - Wow, this is almost turning into a Montego Blue Coupe thread. :lol:
Click to expand...

Never seen so many Montego Coupes in one place! Shame we are not all closer.. could all go for a blast :driving:

Smartbear - Hi, with the mileage on your car this could easily be a sign of a failing ccv system.
Are you burning oil/have sooty tail pipes?
Rob
Click to expand...

The car does burn oil but it's not got any worse over the 4 years / 70k miles I have covered in it, I would think that if if the CCV were to fail, I would notice a dramatic difference in the usage of oil? I would say on average (Depending on how I drive it) I burn 1ltr every 2500-3500 miles. which according to BMW is well within "Spec"

andyfanshawe - HI coupedan.
Good to hear your car passed its MOT though.
Regarding the near threshold Lambda reading.

If you genuinely want to find out why the reading was close. and not speculate, find a garage who is conversant with the live data given from the O2 sensors, pre and post CAT. Also with short and long term fuel trims.

Shouldn't be too difficult to assess the performance of the various sensors.

i do an oxygen storage test, that involves sending the mixture rich and looking at how fast the o2 sensors react with an oscilloscope.

More accurately, how long it takes the post CAT sensor to drop lean when the rich mixture is removed, and compare it to the pre CAT sensor. This will accurately determine if any CAT is struggling.

Not cheap, but conclusive.

Alternatively, get a bottle of CATACLEAN and follow the instructions on it. Cost is about £15 and well worth it. Trust me on this.
If you don't believe me, or are skeptical, type in cataclean reviews and prepare to be amazed.

Additionally, make sure the oil and filter are changed regularly and as stated above, any crankcase ventilation systems are clean and clear.

Any slight exhaust leaks will also affect the lambda readings.

Hope all this helps!
An alternative to all this is to enjoy the car and worry about it next year!!

Andy.
Click to expand...

Hi Andy,
Thanks for this information! I actually have got some BMW software on my laptop (Inpa, DIS, SSS and so on) I'm not entirely au fait with how to use this, but I am wondering whether I could conclude the live lambda readings myself.. Failing that, then yes, it is a good shout to get a garage to do it.

I shall have a look into this CATACLEAN - how does it work exactly, is it a fuel additive or something like the "Terraclean" things where they pump it around the engine to clean carbon build up?

I shouldn't have any exhaust leaks, I recently had the connection from the downpipe to midsection corrode but this has now been fixed and there were no further leaks.

Cheers.
Dan.
 
cataclean is a fuel tank additive and is amazing stuff. Saved many of my customers a big cat purchase. Including my z4 cat!

https://www.cataclean.com/

I have INPA but, like you, havent used it much. I use snapon verus to watch the o2 sensors in action.

The lambda reading is a calculation based on the emissions. Yours is still good. If you have it checked again, make a note of the CO, HC and, if you can, the oxygen content. NOx readings also if you can find a machine to do it!

Put that CATACLEAN in!!
Andy.
 
You must log in or register to reply here.
Back
Top Bottom