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Discussion Starter #1
Ive recently had my 2001 W reg Alfa Romeo 156 in for its MOT on monday gone, and it failed mainly cause of 3 worn tyres and on the Exhaust emissions mainly Carbon Monoxide, so today got it rechecked they fitted new tyres on, but failing it again on the emissions, they beleive that it could be something internal in the engine has its producing a lot of fumes etc, has anyone any ideas, they checked air filter and a few other things.
 

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Lambda sensor(s). Think there are only two on 2000 MY 156s.

Possibly a faulty MAF allowing it to over fuel, or a faulty temp sender making the EC think the engine is cold when it isn't.

"Somthing internal" is unlikely if the engine runs ok but I guess in theory it could be a headgasket although that would show up in other ways too.
 

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Get it on a diagnostic computer and check the outputs of the o2 sensors, maf or map and coolant sensor. If they're all ok start looking at getting prices on catalytic converter. A hole in the exhaust system can also put the co content up.
 

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The guys doing my MOT say it aint the cat converter and i had a replacement lambda sensor, it passed on all other emissions tests. Might take it into my local alfa garage for a diagnostics. I do get times when im driving my car shudders and acts like its about to shut off in most gears.
 

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so what were the emmision results?
1st fast idle test, 2nd fast idle test and idle (co, hc and lambda)
did they carry out bet test? and was the oil temp messured or was it bypassed?
 

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Discussion Starter #6
1st Fast Idle Test

CO - Reading at 0.51% when the limit is .30%
HC - Reading at 125ppm, limit is 200ppm
Lambda - Reading at 1.02, range is 0.97-1.03

2nd Fast Idle test
CO - Reading at 0.47%, limit is 0.30%
HC - Reading at 116ppm, limit is 200ppm
Lambda - Reading at 1.02, Limit between 0.97-1.03

Natural Idle
CO - Reading at 0.49%, limit for this one being 0.50%

Oil Temp was 98 degress C and minimum it should be was 80 degrees C, that is all the test it looks like they have run during the MOT, they said they wouldnt do the tests again when i got the tyres fitted as it would fail, so ive booked it in for Wednesday for a detailed investigation.
 
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