mot emissions fail
Discussion
hi. new here and female driver so all this techinical talk is wasted with me. took my car for its mot yesterday. s reg audi A3. runs fine but had noticed it had a fumey smell when running if i stood round near the boot. anyways failed yesterday on emissions. he checked underneath the car and straight away noticed that some wires that should be connected to a sensor in (or on) the cat?? had been cut which he thinks has caused the high emissions. emisssons reading is as follows
fast idle test co 0.71 % HC 222ppm (pass is 0.30 for co and 200ppm hc)
then strange upside down v reading 1.044 (pass is between 0.970 and 1.030)
second fast idle co 0.43 HC 258 and upside down v passed that one with reading of 1.019
natural idel test passed
tester says i def need new sensor thing which is being done friday (165 squids eeek) and may possily need new cat if that doesnt solve it. whats the chance of me not needing a new cat and why the h3ll would someone cut those wires in the first place??? had it plugged into computer thing a few weeks ago for abs light being on and it never said anything about a sensor being wrong on cat
fast idle test co 0.71 % HC 222ppm (pass is 0.30 for co and 200ppm hc)
then strange upside down v reading 1.044 (pass is between 0.970 and 1.030)
second fast idle co 0.43 HC 258 and upside down v passed that one with reading of 1.019
natural idel test passed
tester says i def need new sensor thing which is being done friday (165 squids eeek) and may possily need new cat if that doesnt solve it. whats the chance of me not needing a new cat and why the h3ll would someone cut those wires in the first place??? had it plugged into computer thing a few weeks ago for abs light being on and it never said anything about a sensor being wrong on cat
Have you had the car long?
If not it may be that the previous owner fitted a de-cat pipe in place of the cat and just chopped the wires. Then before selling it, fitted the cat back on again.
As for the condition of the cat now, best to just suck it and see how it goes once the sensor's been replaced.
If not it may be that the previous owner fitted a de-cat pipe in place of the cat and just chopped the wires. Then before selling it, fitted the cat back on again.
As for the condition of the cat now, best to just suck it and see how it goes once the sensor's been replaced.
ive only had it since end of november. my other car died on me. apparently anti freeze is very important oops! what are thie signs and symptoms of failed cat? its seems pretty efficeint on petrol and has plenty of power when i accelerate and someone has said id lose all that it the cat was broken
Poor emissions are a symptom of a failed Cat.
The sensor in the exhaust is an oxygen (aka lambda) sensor that reads the amount of oxygen in the exhaust gas and the ECU will then alter the amount of fuel (Air fuel Ratio) being used.
When the sensor is broken or disabled the ECU plays safe and uses an excess of fuel. Long term this can damage the Catalyst.
New oxygen sensor(s) and an Italian tune up can often bring them back though.
The sensor in the exhaust is an oxygen (aka lambda) sensor that reads the amount of oxygen in the exhaust gas and the ECU will then alter the amount of fuel (Air fuel Ratio) being used.
When the sensor is broken or disabled the ECU plays safe and uses an excess of fuel. Long term this can damage the Catalyst.
New oxygen sensor(s) and an Italian tune up can often bring them back though.
You can get hold of second hand CATs if it is essential.
It could well be that the Lambda is not functional but if that is the case then there should be an engine management light on the dash. Are there any warning lights on?
As another poster said, there a chance the car was run with a decat pipe but it is standard practice to have a decat with the lambda in and not cut it off.
It could well be that the Lambda is not functional but if that is the case then there should be an engine management light on the dash. Are there any warning lights on?
As another poster said, there a chance the car was run with a decat pipe but it is standard practice to have a decat with the lambda in and not cut it off.
nope no engine management light on. only light thats ever been on was abs and that was sorted a few weeks back with 2 new wheel sensors. the guy who mot'ed it for me said a new cat will be 122 pound plus 40 to fit it so it wont be as expensive as i thought it would be. but could really do without spending the best part of 400 if both have to be replaced. i shall be living on bread an jam for a while i think
There are 2 lamda sensors, precat looks at whats going on in the engine and tells the ECU, a second after the cat to see if the cat and engine controls are working. it sounds like you have either had a decat or the cat failed and they bodged the 2nd lamda to overcome it by fooling the EML. I dont know when the 2nd lamda was fitted, the X plate Fiat no, 53 plate TF yes. its possible for the cat to get poisened and stop working without breaking up inside and strangling the power.
ive just ran out and checked what lights come on and off. when i turn the key in the ignition there is a grid of 6 lights but only 4 come on then they go off again a few seconds later. should the engine management ligh light up each time i put keys in becasue i cant see that light at all? i seem to remember onmy old car it came on then went straight back off again.
dmari26 said:
ive just ran out and checked what lights come on and off. when i turn the key in the ignition there is a grid of 6 lights but only 4 come on then they go off again a few seconds later. should the engine management ligh light up each time i put keys in becasue i cant see that light at all? i seem to remember onmy old car it came on then went straight back off again.
Yes it should light up then go off a few seconds after starting the car.It sounds as if someone has pulled the bulb to hide a fault.
dmari26 said:
nope no engine management light on. only light thats ever been on was abs and that was sorted a few weeks back with 2 new wheel sensors. the guy who mot'ed it for me said a new cat will be 122 pound plus 40 to fit it so it wont be as expensive as i thought it would be. but could really do without spending the best part of 400 if both have to be replaced. i shall be living on bread an jam for a while i think
That is extremely cheap for a new cat which means it will be a poorly made aftermarket part that contains the absolute minimum of the precious metals that are required. It might get you through one MOT, but you may well struggle with the next one.With luck you won't need it anyway, and a new oxygen sensor will fix the emissions. It's surprising that no fault light was illuminated though, does the light come on for a few seconds when you switch the ignition on as it should? If not, the bulb may have been removed by previous owner to cover up the fault.
sounds like they removed the bulb then. it was hooked up to the diagnostics not long after i got it due to abs light coming on but it never brought up a fault on that about this sensor thing. it did bring up a fault that was just numbers and letters but didnt say what it actually was like it did with the abs fault it brought up. they guy who sold me it really saw me coming didnt he!!! really must take someone with me next time i go test drive a car!
If there is no engine management light coming on when start up and the goes off then the bulb has been removed. The reason why the mechanic didn't say anything about the sensor because he was fault finding a abs fault which has a seperate section on a diagnostic machine so would only be related to abs not engine.
It looks like the cat has been removed the refitted like what previous posters have mentioned, also 160 quid for a lambda sensor no way 60-80 quid tops depending on the price for the part they are easy to replace like wise on the cat the price would be for a aftermarket one which aren't worth bothering with get a genuine cat. Saying that if the previous owner has been playing around with it best to get rid and find something better.
It looks like the cat has been removed the refitted like what previous posters have mentioned, also 160 quid for a lambda sensor no way 60-80 quid tops depending on the price for the part they are easy to replace like wise on the cat the price would be for a aftermarket one which aren't worth bothering with get a genuine cat. Saying that if the previous owner has been playing around with it best to get rid and find something better.
Take it for a good motorway run after fitting the new sensor - get the cat nice and hot. This will also give the ECU time to sort itself out.
Same thing before the MOT...heat is the key to low emissions where cat's are concerned.
Ask the MOT man nicely if he'll do the emissions test first while it's still hot.
Same thing before the MOT...heat is the key to low emissions where cat's are concerned.
Ask the MOT man nicely if he'll do the emissions test first while it's still hot.
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