Simon C

Cars just failed it MOT on the dreaded emmisions. (MY96 Sport)

I can't undertand it, the test station said their machine lit up like a chrismas tree during the test. It had a new cat 25k miles ago, spark plugs are gapped correctly and a new Lambda anout 3 months ago.

Results are
Fast Idle
cO2 = 0.54%
HC = Pass
Lamdba = 1.06

Much the same for the second

Idle
Co2 = 0.72%

They also say the exhaust has a minor leak. Could the leak cause this?

MOT runs out tomorrow, is there anywhere I can get this sorted in the next 3 days (MOT runs out tomorrow). I need the car for the weekend and preferably sooner.

I deffo need it sorting by Monday. I'm getting a new car in 3 months so don't want to spend a huge amount on it.

Coffin Dodger

The leak could throw the Lambda reading out.

stephen beynon

iTrader: (7)

where are you based mate

Simon C

South Beds, but I think I might have found the reason!!

This the air filter, the clean colour can be seen in the bottom right!!



I could have sowrn I checked it when I moved 12 months ago (now do a 250 mile a week commute), which means there is a shed load of carbon / soot being pumped onto our roads!

scooby1doo1

iTrader: (7)

Looks like you found it, good luck.

Simon C

Wasn't the filter, with it cleaned it ran richer!!!

I swear this is payback for changing it later this year.

Alan Jeffery

Check the lambda voltage to see if it's cycling. If you don't know how to do that, you have no business working on it, so find a man who can. If the lambda sensor is ok, check for exhaust leaks, as the lambda reading shows a lean mix. The CO is only slightly high, which means your cat is either duff or missing. If you want to ring me to discuss this, I don't mind! 01752 345880 office hours.

Simon C

I can measure it but I don't think my DVM is was it once was as its not cycling teh display quick enough to catch it.

The AFR guage thats wired directly to the lambda input cycles, and almost hits full scale deflection.

The lambda is only 3 months old and OEM from Subaru. Cats only 3 years old and 30k miles if that.

ZEN Performance

Almost always a combination of lambda sensor and a CAT that isn't properly up to temp.

The leak, if near the backbox will raise the measured lambda, so the real lambda could be closer to 0.9 which would certainly point to the factory lambda sensor being goosed or if it was a universal unit it may have been incorrectly wired to the factory connector.

Simon C

Alan, cheers for speaking to me

Zen, bingo, the hole is on the hanger on the mid section, which is being fixed tomorrow.


If that OEM sensor is goosed, my local dealership aint going to like me, as it was bought 28/11/08!!!!

Ginge !

iTrader: (1)

water temp sensor can also cause the car to over fuel too thinking the car is cold, leak in the exhaust sounds more possible now, either that or theres another issue with the car thats killed the new cat you have, does it rattle and have you seen the inside if the cat, if someones used exhaust paste before the cat when it hardens it can act like bullets and but the ceramic core of the cat, also blocked cat is another reason too

Ginge !

iTrader: (1)

what was the readings before and after the lambda was fitted ?

Simon C

Old lambda was dead, threw a cel and everything!!!

Fan cuts in and out.

joz8968

iTrader: (13)

Indeed Paul, as only we know all too well, when my car was MOT'd last Aug. (appreciate your Herculean effort in getting it through, btw).

Simon C

The verdict is the cats dead.

Just failed again, lambda ok now, just but CO was still way to high. The cat should have been warm after a 25 mile blast down the A1.

joz8968

iTrader: (13)

How many minutes gap between the journey and testing, though?!

Simon C

About 3!

joz8968

iTrader: (13)

Fair enough.

Did you really use loads of boost and redline it a lot, though i.e. drove it like an Italian lol?

Simon C

No boost cos it doesn't have any

Lets just say I was pushing over 4k rpm in 5th.