Dreaded mot! High co2😡

[Danny172]

Hey all
Just had a fail on mot for high co2, failed being .5 (should be .3).
To be fair the car is running quite rich to the point the exhaust at idle stings your eyes!
The cars always had a lumpy idle, but drives great!
I’ve literally had to get back to work, so I got back to dropping the car off and sprayed some carb cleaner around the vacuum hoses I could see, plus on the intake bellows after the maf sensor.
Ive ordered a replacement ccv valve and the hose that goes to the rocker cover as it’s quite squashy! The idle did seem a little better when I unplugged the maf sensor, but didn’t have time to drive as couldn’t be sure, although the exhaust didn’t seem so fumy!
I have a smoke pro at work so will give this a try on the vacuum hoses.
The maf sensor seem very expensive on these? (EBay)…would anyone know where I could acquire a good used one? I’m in dover.
Sorry for the rushed explanation, but I need to get back to work!!
Thank you

 

[Stevo7682]

Which engine do you have
Stephen.

 

[Scooblitz]

Hi Danny

From a quick scan through your previous posts, it looks as though you have an M44 Engine 1.9i car. I can see you also previously had some engine idle issues. This was the same with my own M44 and is very common for these cars to run rich and fail an emissions test.

@spurs fan in a coupe Can provide a used MAF sensor if needed.

Are there any engine codes for the car that perhaps indicate a busted Lambda Sensor? This could be a culprit if the ECU isn't getting the right info to the injectors and spraying too much fuel in.

To get it through an MOT, a new CAT will probably work. The cheap ones dont last long and will need to be replaced for every MOT. Remedy this by fitting a decat pipe from ebay for 99% of the year and fit the cheap non oem CAT for MOT each year.

My buddy @Stevo7682 has had some issues with his M44 and used a Euro type 4 approved CAT to deal with the smogging issues. I think there is a write up somewhere with this on the forum. This seems to be as good a fix as possible as an OEM BMW cat is £1000+.

GL.

Scooblitz

 

[Scooblitz]

Which engine do you have
Stephen.

I knew you would be along shortly.

 

[Stevo7682]

I knew you would be along shortly.

It's lunchtime so lurking on here.

 

[Stevo7682]

Right if a m44 1.9 then check all vacuum pipes for splits.
As Stevie has said aftermarket euro 2 cats last about 10 minutes .
I found a guy in Germany who does a m44 front pipe fitted with a higher quality type approved cat which at the moment seems so much better than what I had.
If all other checks are OK then fairly likely the cat will be the issue but vacuum pipes and sensor checks first.
Stephen.

 

[Danny172]

Sorry guys! Yeah it’s the m44 1.9…thanks for the replies!…I’ll take a look

 

[Ianmc]

The only way I could get my M44 through the MOT 3 years ago was to purchase a new BMW OEM cat. Tried 2 new "reputable" after market ones at the time to no avail, but it was third time lucky (at significant cost). Has sailed through last 2 years. Hope you have better luck than I!!

 

[Danny172]

Hi all! Many thanks for the replies!
The car idles steady, but is lumpy…I.e sitting inside the car you can feel the car rock..not by any means bad, but certainly not smooth!
When I unplugged the maf..I’m 80% sure the over rich smell from the exhaust disappeared, the idle certainly felt smoother…but it was a quick test.
The smell from the exhaust is definitely an over rich condition, it certainly makes your eyes water!
my plan of action is to smoke pro the vacuum lines to see if all ok there, then fit the replacement ccv and hose, read codes…although all I have is the creator 110+, clean the maf sensor…I’ll keep you all posted!
I certainly hope it’s not the cat, but correct me if I’m wrong, used to be a bad egg smell when they fail, or a metallic sound when hit?
I wonder if the over fuelling situations go unnoticed and eventually “poison the cat”?…just my theory.
Thanks all

 

[t-tony]

Rough idling suggests a slight misfire and that would raise the HC content through unburnt fuel. What was the HC reading, assuming they gave you a print out of the test result?
Also, be wary of cleaning the Maf sensor as that can kill them off. Do not buy after market off eBay os Amazon etc. they rarely last it they work at all.


Tony.

 

[Danny172]

Rough idling suggests a slight misfire and that would raise the HC content through unburnt fuel. What was the HC reading, assuming they gave you a print out of the test result?
Also, be wary of cleaning the Maf sensor as that can kill them off. Do not buy after market off eBay os Amazon etc. they rarely last it they work at all.


Tony.

Hi tony
I’ve left the printout in the car…in disgust lol!
I’ll put the info up when I go out to it
Mira not necessarily a rough idle…the idle is smooth enough, just a lumpiness to it…the only thing I can liken it to, like an old v8 engine!

 

[colb]

Ideally scan the car and then look at live data fuel trims when car is fully warmed up, high readings would be an indication of air leaks which the car is seeing as a lean mixture, to compensate it will be adding fuel to richen the mixture. It will keep doing this until its adding 20% more fuel then give up and set the EML on the dash. Air leaks across the whole vacuum system should be checked for splits or holes in all the rubber hoses and boots, replace any that are found to have damage. Smoke test should find hard to find leaks. A bad Maf could also be the cause of high fuel trims if its misreading the volumn of air passing through it. The exhaust sensors will pick up more air in the exhaust and compare it with what went through the Maf, thats where it will pick up the mismatch and alter the fueling. Maf's do not always set fault codes, if you replace only use Bosch or Siemens brands do not use cheap chinese ebay Maf's they don't work or last long.
M44 is known for lumpy idle but as long as everything mentioned is ok it will be acceptable.

 

[Danny172]

Hi all!
Plan to look at the car tomorrow night…but I. The meantime I’m internet trawling, and one thing sprang to mind…coolant temp sensor?
How can I tell if it’s gone bad? Do they throw a code or illuminate eml? Would stand to reason if the cars running rich?

 

[colb]

Temp guage on dash wouldn't be reading if the sensor has gone bad, you should be able to view the water temp in live data on a scanner to see how hot its running at. The fuel trims need viewing to see what they are doing use live data on a scanner.

 

[Danny172]

Thanks for the reply.
I did wonder if it would affect the actual gauge reading? It’s just I read that it was a 2 way sensor, sending signal to ecu for cold start mixture, and to dash.
it was just the symptoms I have would point to a diff sensor I.e rich running and lumpy idle

 

[Trevor /chedder]

I've just failed mine, but the tester found a crack in my new exhaust, I've changed it for a new one. Was also fairly sure the temp sensor was sticking, this has led to a cooling system refresh. Hoping all that plus a hot run will get me through next week!!

 

[Danny172]

Hi all thanks for the replies!
Well I had an action plan..but it fell short when my code reader failed to connect to the car! I think the adaptor plug 20 pin to obd (cheapo eBay) has a bad connection, as it’s previously worked fine?
Things I’ve done so far
Replace the ccv and breather hose (old one all ok)
Replaced engine oil and filter
Run cataclean through the system and replaced the plugs ( suspiciously very clean after 1500 miles?
Carried out a smoke pro test on the intake system, all good
I have convinced myself it’s running rich, as when the car idles you can smell it from the exhaust tail pipe ( although the plugs were spotless?
Or faulty injectors as the engine oil (1500 miles) is very pungent of fuel, smells like old 2 stroke oil!
I’ll try for a re test, and if it fails again, I’ll try and put it in somewhere

 

[t-tony]

Try some electrical contact cleaner spray on the socket under the bonnet before giving up on the code reader. I haven't yet had one where I didn't need to do this.

Tony,

 

[Danny172]

Try some electrical contact cleaner spray on the socket under the bonnet before giving up on the code reader. I haven't yet had one where I didn't need to do this.

Tony,

Thanks tony, I did give this a try and it didn’t work.

 

[Danny172]

Heads up…it passed, but only just!