My Brava has failed its MOY due to high lambda reading,
eng speed 2789 pass
co 0.000 pass
hc 15 PPM pass
lambda 1039 fail.

I then had the car serviced, took it back and it still failed. I booked it into fiat, explaining the problem, and they assured they could diagnose it.
I then spent a day at FIAT , who said there was nothing wrong with it as it was within spec.
I suggested they chage the lambda senso(o2), BUT THEY SAID JUST PUT SOME CLEANER IN IT. I said have you checked the emissions, and it appears they would need to borrow one.( I overheard this on the phone).
Anyway they put the additive in, assured me it would pass, and tht they had checked it.
Drove 30 miles back to the test cntre, and yeo, it failed, only worse than before. Any suggestions (Im toying with a rag in the air filter to richen the mixture),

Thanks

Fish

how many times they test it? at my place if if fail they keep trying an usaly it passes after 2 or 3 goes, did they do the test when car red hot?

They tried 2 or 3 times, while I was watching, it did drop down but not emough. Car was red hot, as I had just driven 30 miles from my "local " Fiat dealer.

Fish

Just a thought, but yesterday I only drove 1 mile, and the readings where better.

it usaly better if you threas it before hand, also a bottle of add to petrol injector cleaner can help
btw welcome to the forum

You have an air leak in the exhaust.

Co reading is very low, showing the catalytic converter is working all ok as cats wont reduce co below 0.30 without being up to temp.

HC reading is also low again indicating cat is working all ok.

lambda figure is high showing excess oxygen, catalytic converter uses almost all the oxygen left in the exhaust to reburn co, so excess is most likely coming from a leaking exhaust pipe.

The reason the reading is better after only driving a mile is that the mixture is still rich so compensating for the air leak.

Thanks, I had a new exhaust fitted though (same day as test), all except down pipe I think, and I cannot visually see any holes. I asked the guy to check it on the ramp and he put his hand over the exhaust whilst running and there was a small leak after the sensor, which he replaced.
Could it be the lambda sensor being dirty or conatminated, causing it to be sluggish?
Would a rag in the airbox richen the mixture, just to pass the test?

Fish

Definate air leak on exhaust side. If the leak was on inlet then the lambda sensor would pick it up and the ecu would adjust mixture to compensate. Ask dealer to do a four gas test. Co should be below 0.20, HC below 100, Co2 as high as possible typically 14.9-15.5, and oxygen should be 0.10-0.30.

OK going to recheck the exhaust tommorow.

Fish

Re-checked the exhaust (with soapy water) and found it leaking between the manifold and downpipe. Unfortunately no gasket at MOT centre, so looks like being Monday, hopefully thats it thanks.

Fish

seal it up with a bit of gum gum, just for mot

NumanR said:

You have an air leak in the exhaust.

Co reading is very low, showing the catalytic converter is working all ok as cats wont reduce co below 0.30 without being up to temp.

HC reading is also low again indicating cat is working all ok.

lambda figure is high showing excess oxygen, catalytic converter uses almost all the oxygen left in the exhaust to reburn co, so excess is most likely coming from a leaking exhaust pipe.

The reason the reading is better after only driving a mile is that the mixture is still rich so compensating for the air leak.

Click to expand...

have repped this, handy advice