2000 Jaguar XJR - failed emissions test?

[Finn]

Cheers!


My XJR failed emissions test today as the fast idle Lambda value was higher than max allowed. Everything else is OK, car drives perfect, has steady idle and has normal MPG and so on.

Tester told me that Lambda value tends to be high if the is an intake or exhaust leak. XJR had full specialist head repair last year because of leaking head gaskets so I don't think that's where the problem is. However there is an exhaust leak between center muffler and left side rear muffler. The exhaust leak can be felt by hand.

My question is how sensitive Lambda value tends to be ie. could this exhaust leak be enough to cause this?

 

[Trav]

You have a Stoichiometric value of 15.87-1 which is lean. Look for a vacuum hose leaking or disconnected, a loose clamp or small split in the air intake hose from the air cleaner box after the MAF sensor (if used) a exhaust leak at a connection before the A/F monitor, seeing as this had head work done look carefully at the exhaust manifold to head connection.

Use a vacuum pump with gauge to check vacuum powered controls that may have developed a leak examples of this would be heater controls, vacuum storage cans, brake boosters, etc.

Edit: Generally only leaks pre A/F monitor will effect A/F ratio (Lambda)

 

[Finn]

Thanks for your reply.

FWIW, I failed to tell that this measured Lambda value of 1.08 is not from any of the car's own lambda sensors but measured from exhaust outlet end with a sniffer pipe to analyzer called PKA3.

 

[finmile]

Here's two videos on finding a vacuum leak.

 

[Trav]

Okay I thought they were checking lambda by OBDII, then yes the leak at the muffler is definitely an issue that needs to be addressed as that will affect the value at the exhaust probe.
I see some machines now that use a 4/5 gas analyzer and dyno along with OBDII check.

 

[Finn]

Sorry Trav for misleading in first post - I'm old.

We'll fix the exhaust leak first and check for possible other exhaust leaks as well. If that does not cure it we'll investigate more, in that case XJR probably needs to be checked with computer.

Finmile, kiitti linkeistä.

 

[Leo99]

How did you calculate the stoichiometric value of 15.87?

 

[Trav]

Multiply by 14.7 his is actually 15.876 but I drop the last digit.
The acceptable rage for his test is 14.25 - 15.14

Edit: This is not a good way of doing that part of the emission test, his engine may well be within acceptable range but a small leak after the A/F monitor is giving the probe a false reading. It can be argued that a small leak/weep in the exhaust system is also unacceptable but that should be a separate part of the inspection and not result in an engine emissions failure because it really isn't.

 

[FermeLaPorte]

Are you one of those lazy dudes that change their oil every 10k "becuz PUP can go that far" and use the oil filter twice? Because that may be the reason

 

[kschachn]

Originally Posted By: FermeLaPorte
Are you one of those lazy dudes that change their oil every 10k "becuz PUP can go that far" and use the oil filter twice? Because that may be the reason

Using that logic, it may just as well be caused by his brand of windshield washer solvent.

Another great post from this user.

 

[GenesisGuy70]

Originally Posted By: FermeLaPorte
Are you one of those lazy dudes that change their oil every 10k "becuz PUP can go that far" and use the oil filter twice? Because that may be the reason


Um. What?

 

[SatinSilver]

I think the heat in TX may have fried some brain cells.

 

[Dyusik]

Originally Posted By: FermeLaPorte
Are you one of those lazy dudes that change their oil every 10k "becuz PUP can go that far" and use the oil filter twice? Because that may be the reason


Huh??

Originally Posted By: SatinSilver
I think the heat in TX may have fried some brain cells.

That's the only sense I can make of it...

 

[finmile]

You could check your long term and short term fuel trim values with an OBD2 reader. If the values are high, it could indicate a vacuum leak. If the fuel trim values are normal, then maybe the reason could be a dirty or worn out MAF sensor? Your HC values (unburned fuel) are a bit high, so could there be some problem with the spark plugs? When have you changed them?

Originally Posted By: Finn
Finmile, kiitti linkeistä.

Ole hyvä

Mullakin oli pakokaasupäästöt veitsenterällä katsastuksessa pari viikkoa sitten: Labda oli 1,025. Sen takia tuli vastikään googlettua mahdollisia syitä jotka lambdaa voisi kasvattaa.

 

[Trav]

That's true but they are testing the A/F ratio with a tail pipe probe. The A/F stoichiometric is probably okay but it is worth checking but don't go chasing ghost around when there is a leak in the exhaust which is the likely culprit.

 

[Finn]

FWIW, the problem was faulty heating circuit on right upper oxygen sensor. It was changed today at the Jag dealer and emissions tested good and car now passed yearly MOT.

A bit tempted to trade Jag in for a C5 if I would come across a decent one.