Technical M.O.T Failure (emmissions)

[hixy]

well my car failed it's mot on friday due to c02s being slightly high. Im told it was only just over

He took it round the block to get it a bit hotter but still wouldnt go through.

So i need help as I am skint at the mo they said they think its the lamda sensor but can't be sure.

possible causes!

Before I got it the airbox was cut off and was replaced with a K & N, there is a few wires behind it that seem to have been cut??

Possibly the cat?

the lamda sensor??

I dont really want to pay to have diagnosed if I csan help it.

also a local tester has told me to take it to him and he will probably be able to get it through with some emmissions reducer and getting it really hot??

I don't really know if I should trust him beause he wants the price of another test and he might start failing it on loads of other stuff.

Any help much appreciated.

its a 2001 (y reg) 1.6 bravo sx by the way.

 

[jug]

stick a full bottle of redex in quarter of a tank of super unleaded, then it will pass.

 

[id12586]

Yeah redex will do the job nicely

When i've had my MOT, 4-5 months ago, i was expecting to fail in emmissions.
I was astonished that I've passed and with extremely good results.
One month later, i found out the reason i've made it.
I had the OEM cat for over 120.000km.
I've decided to change it for a Sebring Racing (up to 170bhp) in order to be ready for the HGT conversion.
When i've looked at the old cat, it was in extremely bad shape. I mean it was so blocked, that it hardly left any gas going through it. That was the reason i've got MOT! :yum:

 

[hixy]

cheers for the replys guys.

I heard this might work.

It is going in to be re-tested on thursdady im gona fill it with optimax and redex tonight. whats the chances of it working.

reading was 50 and needs to be 30 to pass?

 

[jug]

i've passed plenty of MOTs using the redex trick after failing badly on emissions, just make sure you have a stong mix of redex, so only have a quarter tank of fuel with a full bottle of redex, also give the car a good hard drive immediately before the MOT, and get the emissions tested as soon as you arrive.

 

[hixy]

ok, so i tried the redex thing and still no joy. so flushed the engine. changed oil, changed plugs and filter tuck it back for a 3rd go but c02s still runnng at about 52.

Its going in for a diagnostics test on tuesday but does anyone have anymore ideas because everyone seems to be stumped and m going to be stuck with out a car as it runs out in a week?

or anyone want to swap for something with mot?

any help much apreciated.

thank you.

 

[jug]

when the redex trick fails it means you really do have a problem.

if lambda is low then you have lambda fault, if lambda is high and o2 is high then you have cat failure, but first check carefully for exhaust leaks at the manifold and flexijoint.



Basic fault finding for advanced emission test failures:

1. If a vehicle fails for high CO at idle and /or fast idle then.... if Lambda is too low, the mixture is too rich. This can be caused either by a misfire or by a faulty Lambda sensor. If it's running very rich, the 02 and HC will be higher than normal.
2. if it has a high Lambda and high 02 (0.5 to 1.5%), the "CAT" could be faulty. Before condemning it make sure its hot enough to work, the Lambda and other sensors are working OK and the exhaust downpipe hasn't got any leaks.
3. if the vehicle fails for high HC then ...if the CO passes, the vehicle is probably misfiring. Or if the CO fails and the Lambda reading is too low, the mixture is probably too rich and it may also be misfiring.
4. if the CO fails, the Lambda reading is high and the O2 reading is high (0.5 to 1.5%) the "CAT" could be faulty. Again check out the simple measures above before condemning it.
5. if the Lambda fails then...if its too high the Lambda sensor may be faulty, the mixture may be too weak or there may be a hole in the exhaust downpipe. If Lambda is too low the sensor may be faulty, the mixture may be rich or the vehicle may be misfiring.

 

[hixy]

there is no air box and apparently lamda is very close to failing but hc is fine? and co is about 55?

will diagnostics tell me exactly what is wrong?

Thanks for all the help guys.

 

[jug]

i'd try replacing the lambda sensor first.

 

[hixy]

i had it diagnosed today and all that came up was a problem with the "map sensor" and they have cleared it and said it may be fixed now.


but i dont no what this is and dont want to pay for a retest if it is going to fail again, can anyone elaborate on this please?


Thanks again.

 

[bandido41]

I thought retest was free within 10 days?

 

[jug]

i had it diagnosed today and all that came up was a problem with the "map sensor" and they have cleared it and said it may be fixed now.


but i dont no what this is and dont want to pay for a retest if it is going to fail again, can anyone elaborate on this please?

the MAP sensor would be illuminating the fuel injection fault light if it was faulty, if your light is not on when the engine is running it means the code is only there because it has not been cleared after a previous fault. that means it will have had no effect on your emissions.

your problem is either lambda, cat or an exhaust leak.

 

[hixy]

ok do you think its most likely to be the lambda, so i should try that first?

also is there any easyway to find an exhaust leek?

 

[jug]

yes i think the lambda is most likely and should be changed first.

the easy way to find an exhaust leak is to stick a cloth in the tail pipe, if the engine doesnt cut out you definately have a big leak and you can then find it easily because the fumes will be forced out the leak. even if it doesnt cut out you need to feel (carefully) for leaks at the flexijoint and at both gaskets (where manifold meets head & where manifold meets downpipe). the flexijoint is a common place for the leak.

 

[hixy]

right just called my local supplier to get a lambda sensor and they are telling me I have two???


is this true? if so is there anyway i can find out which 1 needs replacing as i really dont want to have to waste anymore money by buying 2 at £140?

Thank you.

 

[jug]

there is only 1 lambda on the 1.6.

maybe a £5 scrapyard lambda would be a worth a try, clean it with contact cleaner before fitting.

 

[hixy]

cheers i will give it a shot.

 

[hixy]

jug I am going to get a lambda today. are you sure I only have one because The mechanic that diagnosed it said "both lambdas" are ok also

Its a y reg 1.6 16v sx?

 

[jug]

yes there are 2!
i just checked volume4 of the manual where they describe the changes that were made in 2000. the attached pic shows where they are.

the cat is also in a compeltely different position, the front half of the exhaust is very different.

when you have 2 lambdas, the one before the cat is the regulator and the one after the cat is the diagnoser. if you fail emissions due to a lambda fault it means the regulaor is the problem, if you have a faulty cat the diagnoser notices and illuminates the fault light, you would also fail emissions in this case. the way to decide if its lambda or cat is by the HC emissions, hich HC means overfueling (regulator fault) rather than a faulty cat.

 

[hixy]

ok i understand that so i need the lambda at the front of the car. How ever my hc is fine? its c0's that is failing and lambda that is quite high??