emissions + ovality nct failures

v240gltse

hi all

My daughters 1999 A3 1.8 petrol failed NCT on 2 counts Ovality on front axle ovality and emissions :mad::mad: yesterday.

last year the cat and lamda sensors where both replaced ( as a result of a similar emissions failure ) and passed the nct on the 2nd go .

On the run up to the NCT i used regular mix of Dipetane ( not that I suspected an emission failure ) and carried out a full service but just as a pre NCT clean up.

So from the attached images can someone please help me to interpret them and where to even begin to start the process of accessing if repair is going to out-way the value of the car ?

thanks in advance

brendan

George Dalton

Front discs and pads should sort the brakes issue.

The emissions might be more difficult. There may be a cat problem but there also could be an underlying problem with the engine which is causing the cat problem. Does the engine burn a lot of oil?

v240gltse

hi george

thank for the help. had a check of the brakes and the disks are fine ( no lip on on any of them at all ) would need to remove the wheels to check the pads ( next job to do )

no its not burning oil to a noticeable level and there is no smell of burning oil from the exhaust either.

thanks

brendan

nct tester

you'd really need a dial gauge to check the discs for ovality, visual inspection wont really tell you if they are warped or not. can u feel a pulsing sensation through the pedal during braking??

Nissan doctor

As above, a visual inspection will tell you nothing about any ovality or run out issue with the disks.


A high CO reading on its own indicates that the car is running lean, I.E too much air for the amount of fuel. Having said that, the HC's are pretty high as well although still within tolerances so there seems to be an air/fuel ratio issue.

v240gltse

hi nissan doctor and nct tester

there is no wobble in the steering at any speed and there is no judder or pulling under braking.

keep those idea's coming

brendan

Wheelnut

The lads are right about the brakes regardless of how they look or feel. You need two front discs (the front left is over the limit and the right is not far behind) and of course you should fit new pads as well.

Not sure about the emission problem, any blows (leaks) in the exhaust? I assume the air filter is good because you serviced it.

Syllabus

the majority of cars we see with a CO fail tend to have some sort of leak in the exhaust whether it be a hole or a loose clamp.

lamda looks ok. HCs prob due to age of car/normal engine wear.get the exhaust checked in a garage


imo

nct tester

unlikely a leaking exhaust causing this. vw and audi petrol engines are prone to burning a drop of oil. valve stem seals give a bit of trouble too.

Nissan doctor

Syllabus wrote: »

the majority of cars we see with a CO fail tend to have some sort of leak in the exhaust whether it be a hole or a loose clamp.

lamda looks ok. HCs prob due to age of car/normal engine wear.get the exhaust checked in a garage


imo

A CO or HC issue indicates an AFR issue coming from the engine.

A leaking exhaust causes the Lambda reading to be off.

v240gltse

hi

quick update. mechanic changed the disks and pads for the ovality issue . He also checked for any air leaks but all checked out fine. He removed and cleaned the throttle body and re-calibrated it.

however as he doesn't have an emission reader we cant check if that has had any effect. Does anyone know of a garage in the kildare or south Dublin area that I can have the emissions re-checked ?

tia

brendan

v240gltse

hi

car back from more diagnostic testing and all sensors readings are fine but car still over fuelling like a b*tch :mad::mad::mad::mad::mad:.

only suggestion that the garage mechanic made was it possible if the ecu mapping had been altered in some way as he cannot find anything on his system.

now can anyone recommend someone who check that the correct map is in place or how can teh ECu be reset to use the default map ???

tia

brendan

Nissan doctor

v240gltse wrote: »

hi

car back from more diagnostic testing and all sensors readings are fine but car still over fuelling like a b*tch :mad::mad::mad::mad::mad:.

only suggestion that the garage mechanic made was it possible if the ecu mapping had been altered in some way as he cannot find anything on his system.

now can anyone recommend someone who check that the correct map is in place or how can teh ECu be reset to use the default map ???

tia

brendan

Christ:rolleyes:


The ECU mapping can't be changed just like that.

If the car is overfuelling then it has an issue with the combustion or the air/fuel metering.

dgt

I lol'd :pac:

I'd be looking at how the air is getting to the engine ie the hoses and pipes, are they blocked, perishing etc?

And what method did they use to recalibrate the throttle?

v240gltse

hi

thanks for the replies. as to the throttle calibration I have no idea what was done and there is as he says " definitely no air leaks or blockages in the breather system " .

The only reason for looking at the ecu map is that when it failed the nct last year we discovered that the inside of the cat had been removed and the garage is now wondering if the previous owner had had the ecu modded for power etc etc.

Last year that many parts were replaced that my wallet cried but everything was fine and flew through the test and i honestly thought the same would happen again this year, boy was i wrong.

i know that the ecu mapping is not easily done but it CAN be done and i would like to know if the default one is in place or not as this problem is driving me mad, so much has been done and its fast becoming an non-economical problem that cant be solved and i dont want to pass on a crock of sh1t to some other poor soul.

keep those idea's coming

dgt

Did you replace the cat?

Nissan doctor

v240gltse wrote: »

hi

thanks for the replies. as to the throttle calibration I have no idea what was done and there is as he says " definitely no air leaks or blockages in the breather system " .

The only reason for looking at the ecu map is that when it failed the nct last year we discovered that the inside of the cat had been removed and the garage is now wondering if the previous owner had had the ecu modded for power etc etc.

Last year that many parts were replaced that my wallet cried but everything was fine and flew through the test and i honestly thought the same would happen again this year, boy was i wrong.

i know that the ecu mapping is not easily done but it CAN be done and i would like to know if the default one is in place or not as this problem is driving me mad, so much has been done and its fast becoming an non-economical problem that cant be solved and i dont want to pass on a crock of sh1t to some other poor soul.

keep those idea's coming

I'd be very surprised if someone had performance mapped a car like that.

The gains would be minute for the expense.

v240gltse

hi dgt

The cat was installed ( generic not audi part ) ,maf (audi ) , lambda sensor (audi ) were replaced last year in order to cure the problem.

regards

George Dalton

Those generic cats typically have a lifespan of only a year or thereabouts so you could well be looking at a cat problem.

What part of Kildare are you in?

v240gltse

hi george

pm sent

v240gltse

hi all

sorry to drag up an old thread of mine but i decided to get the emissions checked again after the new cat was fitted back in Feb just as a precaution. The SUN DGA2500 diagnostics shows a fail on CO% vol as follows:

test 1

max limit 0.2
measured 0.66
result: fail

test 2
CO %VOL

Max limit 0.5
measured 0.694

also see attached report for some more info . Its hard to believe that a car can be going through catalytic Convertors at a rate of knots like this or is there something else causing the problem ???

thanks in advance

brendan