MOT failure emissions

[mr2mark]

well thats your problem....... I had an audi today that failed ..... I'd picked it up from about a mile away where it had been parked all day..... I revved it around 4000rpm for a good 30 secs..... set the computer away again and it was fine ..... Its called "conditioning the catalyst" .... The tester should always have the car at normal operating temperature.

[Anonymous]

Probably difficult to say but how long would it take for the cat to reach operating temperature?
The other day at the garage I'd driven the car for a couple of miles to get there and it was then revved for about 5 minutes in total while he watched the reading to see if it was reducing but no change at all.
I'll call my Uncle tomorrow (he works at the dealer that carried out the MOT) and I'll ask him to find out if the car was "hot" first or not.

[mr2mark]

Oh if it was revved for about 5 mins it really should of been at normal operating temp...... it may be your cat ..... but its rare for a cat to knacker ...   s:cry: :cry: s:cry:

[Bongo]

strangely no dealer in the world has ever heard of the pre-cat problem can you say "corporate denial"

When I had a problem with failing emissions on an MOT it was the first thing they checked, citing it as very common thing to happen.

The actual cause for me was the O2 sensor,which had been threaded when we gutted the precats, not sealing properly.

These were my results when it failed:

Fast Idle test:
CO: 0.48% Vol - fail, (<= .30% pass)
HC: 17ppm vol (<= 200ppm pass)
Lambda .990 (pass range: 0970-1.030)

Second fast idle test
CO: 0.47%
HC: 7ppm
Lambda: .990

[Anonymous]

Those figures are very similar to mine then, so the cheapest positive result for me could be a dodgy O2 sensor.
Just a pain having to wait til Thursday to find out!
Incidentally if anyone in the south needs a good independant garage I know just the man. He's had many years experience at a main Toyota/Lexus dealer and now does exactly the same thing but for himself. He charges £25 per hour and is very honest and reliable.
His name is Ian and you can get him on 07833 545240.

[Anonymous]

Got the diagnosis back today. One of the oxygen sensors was knackered. New one will be £132+vat and is being fitted tomorrow. That price sound about right?

[markiii]

for toyota yes

still think they need to check teh bottom opf teh precats to be on teh safe side though

[Anonymous]

The part is from Toyota but an independant garage is fitting so the labour should only be about £30 with any luck. I'll get him to properly check the pre-cats too just to be sure.
Thanks for all the suggestions etc on here everybody. It will be nice to finally get my MOT done and be able to change my correctly spaced number plates back to my mis-spaced ones again!

[Anonymous]

Hooray Im £180 lighter but now have an MOT! Emissions are extremely low now so kind to the environment too!

[Anonymous]

Can someone explain to me why fitting a new sensor would reduce the emissions enough for this to pass, surely it is just a sensor and wouldn't have any effect on what the actual emissions were?

[enid_b]

i could be wrong (usually am) but here is my understanding

the o2 sensor measures the content of the exhaust gas in 2 places, once before the main cat, and once after it. they feed the measurements back into the ecu, and then it adjusts the mixture of fuel and air, in an attempt to keep the emissions low.

if one of them goes pop, then the measurements sent back are incorrect, causing an inbalance in fuel and air, causing a rich mixture, and dirty emissions.

swapping an o2 sensor could resolve this problem and rumour has it, improve mpg.

HTH

E

[markiii]

nearly

2 02 sensors are used for fuel trim before the precats

1 02 is poist main cat and is there purely to see if teh mixture is different to prove if the main cat is working.

they don't tune for emissions

[enid_b]

lol, furry muff.

knew it was along those lines lol

peace out brothers

(yes ive been drinking stellla again)

[Anonymous]

And what about your sisters?!   s:lol: :lol: s:lol:

[enid_b]

lol, furry muff.

knew it was along those lines lol

peace out brothers - and sisters (thanks) lol

(yes ive been drinking stellla again)

[enid_b]

i could be wrong (usually am) but here is my understanding

the o2 sensor measures the content of the exhaust gas in 2 places, once before the main cat, and once after it. they feed the measurements back into the ecu, and then it adjusts the mixture of fuel and air, in an attempt to keep the emissions low.

if one of them goes pop, then the measurements sent back are incorrect, causing an inbalance in fuel and air, causing a rich mixture, and dirty emissions.

swapping an o2 sensor could resolve this problem and rumour has it, improve mpg.

HTH

E

lol told you i could be wrong......

and i was.

mroe beer pleeez

[trickyD]

i could be wrong (usually am) but here is my understanding

the o2 sensor measures the content of the exhaust gas in 2 places, once before the main cat, and once after it. they feed the measurements back into the ecu, and then it adjusts the mixture of fuel and air, in an attempt to keep the emissions low.

if one of them goes pop, then the measurements sent back are incorrect, causing an inbalance in fuel and air, causing a rich mixture, and dirty emissions.

swapping an o2 sensor could resolve this problem and rumour has it, improve mpg.

HTH

E

Just a question to this (I have same symptoms)
Why doesn't this O2 failure show up as increased HC if it's running rich?
:/

[redarrow]

You lot make me lath a good mot man would
Try his hardiest to get you a pass.

I have a old cat and two Brocken o2
And a cracked pipe for just fun we left the car
Running over 40 minutes untill  you could
Fry dinner off the hood guess what it pass all
Emissions was only a test for fun .....

So i say it the time the tester let the car run  only my opinion

Example my mot man didn't care if he had to reset
The computer 10 times as long as it passes,
If your car pass everything except emission
But the tester can tell the car well looked after
The tester get it thru one way or another

No said it yet ,but it can even be leafs and grime in the air box.

Just stick some redex in the car drive for 40 minutes on a
Long road , then do the mot straight away never ever failed 99% time

When the car starts up is there smoke from exhaust if
So how long till it completely clears

[trickyD]

Makes sense