MOT failure. High Lamba reading ??

AnGarrek

Took my Vectra for it's mot today and it failed on the Emissions test 🙁

The minimum limit for the Lamba is 0.970 maximum limit is 1.030
CO limit 0.300
HC limit of 200

1st fast idle test was a value of 1.085
CO Actual value 0.005
HC Actual value 2

2nd fast idle test was a value of 1.032, just 0.002 over !
CO Actual value 0.002
HC Actual value 0

Natural idle test
CO 0.005

The car has covered 58000 miles, and is standard except a Remus centre section,
and the 3 pipe mod c/w a K&N panel filter.

I'm suspecting the Lamba sensor is either faulty, or isn't sealed well, am I right in thinking this, or is something else at fault dunno..

Jamee

I would have said you are correct mate, the lamba sensors are picky at the best of times.

AnGarrek

That was my 1st thought, but I was unsure if the reading was high because the Lamba sensor was faulty, or something else was faulty making the emissions that the Lamba sensor reads, incorrect ?

TBH, I'm not completely sure what a bl**dy Lamba sensor does :roll:

edit

I've Googled Lambda and a faulty Lambda sensor can result in poor fuel economy ?

Some people have commented that thay've noticed that my car sometimes smell a little rich ?

My average mpg is around 23/24 mpg, not really ragging it, but not driving Miss Daisy either.
My old SRi 140 would return anywhere between 28 & 32mpg under the same conditions, so it's looking like it is the Lambda, is there some way of double checking before I puss out £70 odd ?

Jamee

I think this right, the lamba sensor just checks the gases coming out of the engine.exhaust, and chucks a warning up if the gases are a bit naughty, im sure Daz or vocky will correct tho mate.

vocky

it could be the upper mixture lambda sensor is faulty or an exhaust leak, the reading is lean when it failed

but it could be your exhaust backbox, twin exit exhausts sometimes need one side blocking up to pass the test

Daz

as vocky says either an exhaust leak or ure back box...check for leaks if there aint any i suggest putting a rag over the tailpipe whilst they test it...

AnGarrek

Thanks for that guys !

I have the standard SRi letterbox back box, so I'll rag up one of the outlets for the test.

I don't really want to buy a new Lambda sensor if it's not needed, but my test is out tomorrow, and I can't afford to fanny around for days trying to find the problem,
but the more I look into it, the more the sensor looks suspect.

As I said, my mpg isn't wonderful at the moment, so that combined with the high reading looks like it's probably on it's way out.

Daz

If the sensor was faulty u wud find that ure co reading will be out to... the llambda sensor does not alter ure llambda reading

AnGarrek

Well, if the sensor is ok then that's the 1st bit of good news today 😃

I'll check the system through and repair any leak and rag one of the back box outlets when they test it.

I'm only looking for 0.002 to pass, so fingers crossed, it can't be too much !!!

BTW, any idea why it's a bit thursty on fuel ?
My mate rekons it's the GSi front bumper..................now my Vec looks like a V6, it feels the need to scoff fuel like a V6 :roll:

vocky

a good tip:

take your car for a good long thrash before the mot, it gets the exhaust really hot cheers..

Daz

Mine drinks fuel like its goin out of fashion 2..

blue_se2

Daz said:
Mine drinks fuel like its goin out of fashion 2..

Mine too :roll: but since the 2.4 manifold it's been driven a bit harder :lol: about 24-6 MPG :evil:

Daz

that much neil....