Did you give the car a good run before the test to get it nice and hot. Maybe ask the MOT guy to place the gas probe in the other exhaust pipe. Mine fails if the pipe is in one side but passes when stuck in the other side. Can't remember which though.

 

Yeah i took it for a good run before hand, it was at full temperature. Yeah the test was taken twice and alternating tailpipes. I know that previous TT MK7 exhausts had an issue with sucking air through the passenger side pipe, but mine has the balanced exit valve and doesn't suck any air.

god knows whats going on.

 

If it was genuinely over fueling then you'd have noticed really poor consumption!! Was the car up to full working temperature, usually a good idea to get it hot and hit the redline on the way to the MOT station.... Then dont let it cool down and get them to test it when hot

 

the car is definitely over fueling due to poor consumption and blackening of tailpipes almost instantly. the car was at full running temperature during the test and had been blasted down the bypass on the way there.

 

How long ago did you fit the 52mm TB???

And after you fitted this did you reset the Steppa motor (sometimes confused with ECU reset)??

 

The TB had been done before I owned it so I'm not sure. How would I go about resetting it?

Cheers

 

i did a search and found this

http://forums.mg-rover.org/showthread.php?t=230030

may or may not help, but as its free to try may be worth a shot!

 

Oh right yeah, I have done this but I call it something different. I still believe it's the inlet side so I'll change the green sensor in the manifold and see what happens.

 

When was the air filter last changed?

 

do you think thats significant IanMc ? why? i am not in critique just curious as to reason for asking...

i will say, that my f passed its mot in january, and its filter aint been changed in over 25K miles.. neither have the plugs.. over three years now..

so i am interested in the OP`s fault and what its cause might be. i have never looked at the air filter or the condition of the spark plugs they are just as they were when i bought the car.. and i dint see them then.. ive never looked at them..

 

No problem Incony. As the name suggests, an air filter does just that. That means that over time/miles any filter will accumulate particles deemed not appropriate for the engine internals.

By collecting particles on its surfaces, the filter very gradually loses effect. As the surfaces become clogged the amount of air that can pass freely slowly reduces. Any reduction in the volume of air altering the engine directly affects the fuel/air (combustion) ratio. So, ultimately the mixture will become richer, directly affecting emmisions.

Old man ramble over lol...

 

He has a Vader carbon mesh air filter. I don't think they need washing like k&'s. I have a Vader on my f and its always been OK. Last mot my 97 vvc failed emissions but I think it was down to all the blue smoke on start-up carboning up the exhaust as it passed after a terra clean.

 

so.. ( and i dont want to detract from the OP`s problem) why doesnt, or cant the ecu regulate the amount of fuel to combine with the air available.. ?

you think it ignores less air and just produces a rich fuel mix?

there is less oxygen for example in hot air - its less dense..

there might be just as much oxygen in a smaller sample of cold air.. its denser..

density is key, and is how the ecu determines the mixture?

isnt that why the lambda sensor is important? isnt that what determines how the ecu sets the mixture from what is available? by sensing what is being thrown away?

if the lambda sensor is A1 and the ecu reads it... isnt it an ecu problem if the mixture isnt being burnt efficiently? the lambda sensor is telling the ecu the exhaust has the wrong content? the ecu isnt adjusting it? or.. the ecu is adjusting but delivery is wrong?

so wont there be any error codes to see?

i would check the compression and the valve timing, the condition of the valves.. since what i see is unburnt fuel escaping by lack of complete combustion..?

for some reason the ecu cannot adjust the available mixture correctly.. but if it was lack of air.. the engine would not idle. and if it was bad compression or valve timing.. it would not idle properly either, if it was ecu... then the ecu is ignoring the sensors telling it the mixture is wrong.. it would just run rich...

 

Absolutely no idea lol

 

Boringly I'd suggest getting the car looked at by someone with a T4 so it can be more certainly determined where the problem is

Might as well try the air temp sensor if you have one to swap though ?

By how much is it failing ?

 

It's miles out like 7% on CO's. I still think this must be a sensor fault, I'm going to fit the air temp sensor today. I'll post the outcome, fingers crossed.

 

Hi guys, Just recently had an MOT on my F, and its failed on emissions. I did think that it was running a bit rich but wasn't sure, I've changed the plugs, leads, CAT, coolant temp sensor, ran some redex through injectors, changed fuel filter, changed lambda sensor (pain in the arse) and its still failing on CO's and lambda reading. I've ordered a green air temp sensor as i cant really see what else could be the issue. So if anyone else has had this issue and has some suggestions it would be greatly appreciated. Cheers.

We got exactly the same issue but can't seem to find any solution. Looking at the date of this post, you'll probably resolved your problem. Can you please relate what was wrong? Kind regards, Danny

 

Welcome

MGF2000 hasn't logged into the forum for 9 years so I doubt you will get an answer. Perhaps you would like to go through what the issue is and someone may be able to help.