Failed emissions on MOT. Car is running lean.

FossilFish · Apr 17th, 2013, 17:10

Took our 940 for its test, the car got a few advisories for front pads and bushes, but totally failed emissions didn't get the report but heard figure of 70% carbon monoxidea pass is 20%.

Told the tester I had issues with blocked breather box, he said it could be that, he also said it is running rich(lean) and to adjust fueling. Q. How to I do this is it adjustable?

Diesel-do-nicely · Apr 17th, 2013, 17:24

if it was to lean, it would pass.
if it is to rich it will fail.
either the engine is running in cold start mode. (as if the choke cable had been pulled out for the old timers )
or the cat is not working properly.
But i suspect the engine to be in either limp or cold start mode.
Are the spark plugs black with soot ?
Is your air filter filthy ?

I gave up on a brilliant 940 , m reg, which despite changing almost everything bar the wiring loom , would not get to pass levels.
I had it crushed at the recyclers, as an act of revenge for weeks of wasted money and effort. silly really but i had already in a rage taken a hammer to the engine and smashed its head in.....

rogerthechorister · Apr 17th, 2013, 17:35

You really need the report.

CO results from incomplete combustion - ie not enough oxygen.
CO2 results from complete combustion.
Particulates result from unburnt fuel ie WAY not enough oxygen.

FossilFish · Apr 17th, 2013, 17:43

Thanks for the quick reply diesel-do-nicely, never had this on previous test and last year air filter, fuel filter, fuel injectors where ultrasonicly cleaned, I also had CAT tested and it was working fine. I will make sure injectors are seated properly buy a new filter and take it back for a test on emissions. He said I could clean my breather box and adjust my throttle air mix but we could not see a adjusting screw near throttle cable, I have a slight misfire I did change my leads for recently but find lead closest to dizzy loose I have tryed to use plilers to make it hold better as that one has white tip (not good). Mind you I got a pass (wink wink)

FossilFish · Apr 17th, 2013, 17:50

Quote:

Originally Posted by rogerthechorister

You really need the report.

CO results from incomplete combustion - ie not enough oxygen.
CO2 results from complete combustion.
Particulates result from unburnt fuel ie WAY not enough oxygen.

I have never come across this lean/rich issue I want good MPG and flowers flowing from the pipe but more fuel more power.

The tester said 0.70 Carbon monoxide at idle and high reading on fast idle. He said 0.20 was a pass, I finished a night shift and bit confused. I am not shy to say I am a numpty and I can hide behind this screen.

TonyS9 · Apr 17th, 2013, 19:36

Havn't really had to do this myself, but you want to check the inputs to the fuel mgt like air flow. Is there a DC voltage you can measure? Actually I think the tick over may not use the MAF, so the throttle switch is more important. Not hard to check. Also check the throttle body and look for air leaks in the breathers or manifold.

Then maybe test the O2 sensor, fuel pressure, injector dwell and supply voltage.

Unless the mgt is fked, but thats pretty rare.

rogerthechorister · Apr 17th, 2013, 19:43

The usual bollox is to take the air filter out, take it for a 20 mile thrash down the motorway at a bit over oo-er-ossifer in THIRD to get it nearly into meltdown, then take it in for the MoT.

stephend · Apr 17th, 2013, 19:43

0.70% CO would be in the right ball-park for a car without a cat (the job of the cat is to reduce the 1% or so CO that comes out of the combustion chambers to <0.2% at the tailpipe). So your figures *could* indicate that the cat, for some reason, has failed.

Worth taking your plugs out and checking to see if they're sooty, which would indicate it's running rich, and would put the CO up.

I don't understand what the tester means by "rich(lean)". I guess he means it's not consistent?

bob12 · Apr 17th, 2013, 20:11

When I get my MOT I always get a copy of the emissions info, but maybe that has changed since last August.

FossilFish · Apr 17th, 2013, 20:19

Thanks for the imput , I do appreciate it. I got the exhaust from CAT back last year and I was going to replace the CAT by putting a new aftermarket cheapy one on but the bloke from MrExhaust tested the heat pre Cat pipe and post and said it was the original CAT and its working as it should, and I had a MOT just after and results were normal. Will do a sort the air filter and clean or replace breather box as I have oil weep from oil cap. Hope its not a sensors as they cost many bucks. Many thanks you knowledgeable kittens

Apr 17th, 2013, 17:10	#1
FossilFish Thank fossils for fuel! Last Online: May 23rd, 2024 21:06 Join Date: Jan 2012 Location: London	Failed emissions on MOT. Car is running lean. Took our 940 for its test, the car got a few advisories for front pads and bushes, but totally failed emissions didn't get the report but heard figure of 70% carbon monoxidea pass is 20%. Told the tester I had issues with blocked breather box, he said it could be that, he also said it is running rich(lean) and to adjust fueling. Q. How to I do this is it adjustable? __________________ 'If you are not one of us, you are one of them'

Apr 17th, 2013, 17:24	#2
Diesel-do-nicely Master Member Last Online: May 16th, 2014 08:31 Join Date: Mar 2010 Location: edinburgh	emmision, if it was to lean, it would pass. if it is to rich it will fail. either the engine is running in cold start mode. (as if the choke cable had been pulled out for the old timers ) or the cat is not working properly. But i suspect the engine to be in either limp or cold start mode. Are the spark plugs black with soot ? Is your air filter filthy ? I gave up on a brilliant 940 , m reg, which despite changing almost everything bar the wiring loom , would not get to pass levels. I had it crushed at the recyclers, as an act of revenge for weeks of wasted money and effort. silly really but i had already in a rage taken a hammer to the engine and smashed its head in.....

Apr 17th, 2013, 17:35	#3
rogerthechorister Rogerthechorister Last Online: Dec 16th, 2023 02:15 Join Date: May 2006 Location: Rochester	Too lean? You really need the report. CO results from incomplete combustion - ie not enough oxygen. CO2 results from complete combustion. Particulates result from unburnt fuel ie WAY not enough oxygen.

Apr 17th, 2013, 17:43	#4
FossilFish Thank fossils for fuel! Last Online: May 23rd, 2024 21:06 Join Date: Jan 2012 Location: London	Thanks for the quick reply diesel-do-nicely, never had this on previous test and last year air filter, fuel filter, fuel injectors where ultrasonicly cleaned, I also had CAT tested and it was working fine. I will make sure injectors are seated properly buy a new filter and take it back for a test on emissions. He said I could clean my breather box and adjust my throttle air mix but we could not see a adjusting screw near throttle cable, I have a slight misfire I did change my leads for recently but find lead closest to dizzy loose I have tryed to use plilers to make it hold better as that one has white tip (not good). Mind you I got a pass (wink wink) __________________ 'If you are not one of us, you are one of them'

Apr 17th, 2013, 19:43	#7
rogerthechorister Rogerthechorister Last Online: Dec 16th, 2023 02:15 Join Date: May 2006 Location: Rochester	Usual bollox The usual bollox is to take the air filter out, take it for a 20 mile thrash down the motorway at a bit over oo-er-ossifer in THIRD to get it nearly into meltdown, then take it in for the MoT.

Apr 17th, 2013, 19:36	#6
TonyS9 Premier Member Last Online: May 19th, 2024 20:22 Join Date: Jul 2009 Location: Holywood	Havn't really had to do this myself, but you want to check the inputs to the fuel mgt like air flow. Is there a DC voltage you can measure? Actually I think the tick over may not use the MAF, so the throttle switch is more important. Not hard to check. Also check the throttle body and look for air leaks in the breathers or manifold. Then maybe test the O2 sensor, fuel pressure, injector dwell and supply voltage. Unless the mgt is fked, but thats pretty rare.

Apr 17th, 2013, 19:43	#8
stephend Premier Member Last Online: Dec 23rd, 2023 21:20 Join Date: Dec 2007 Location: S. Wales View Photos By: stephend	0.70% CO would be in the right ball-park for a car without a cat (the job of the cat is to reduce the 1% or so CO that comes out of the combustion chambers to <0.2% at the tailpipe). So your figures could indicate that the cat, for some reason, has failed. Worth taking your plugs out and checking to see if they're sooty, which would indicate it's running rich, and would put the CO up. I don't understand what the tester means by "rich(lean)". I guess he means it's not consistent? __________________ 1989 740 GL 2.0 estate 2000 V40 2.0 (gone) 2005 Toyota Avensis 2.0 estate (gone) 2012 Ford Mondeo 2.2 TDCi estate 1999 Land Rover Discovery 2 TD5

Apr 17th, 2013, 20:11	#9
bob12 bob12 Last Online: May 20th, 2024 19:27 Join Date: Aug 2006 Location: Woking	When I get my MOT I always get a copy of the emissions info, but maybe that has changed since last August.

Apr 17th, 2013, 20:19	#10
FossilFish Thank fossils for fuel! Last Online: May 23rd, 2024 21:06 Join Date: Jan 2012 Location: London	Thanks for the imput , I do appreciate it. I got the exhaust from CAT back last year and I was going to replace the CAT by putting a new aftermarket cheapy one on but the bloke from MrExhaust tested the heat pre Cat pipe and post and said it was the original CAT and its working as it should, and I had a MOT just after and results were normal. Will do a sort the air filter and clean or replace breather box as I have oil weep from oil cap. Hope its not a sensors as they cost many bucks. Many thanks you knowledgeable kittens __________________ 'If you are not one of us, you are one of them' Last edited by FossilFish; Apr 17th, 2013 at 20:24.

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