hc emission problem uk car
#1
hc emission problem uk car
hi i have a my2000 uk subaru and when i had print out of emmisions data the hc were reading 0 co was 0 and lambda was 1.020 what would cause hc to be so low
#2
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Cause of low HC is good combustion!
HC is unburnt fuel (fuel and oil is HC, short for hydrocarbon). CO is carbon monoxide - from combustion with lack of oxygen; the lower the better.
However a reading of zero is a bit odd; To me it suggests the gas analyser was zeroed with the probe still up the exhaust pipe! (it should be removed from the exhaust pipe when auto-zeroing) or the water trap needs emptying.
Basically put, the readings are wrong.
HC is unburnt fuel (fuel and oil is HC, short for hydrocarbon). CO is carbon monoxide - from combustion with lack of oxygen; the lower the better.
However a reading of zero is a bit odd; To me it suggests the gas analyser was zeroed with the probe still up the exhaust pipe! (it should be removed from the exhaust pipe when auto-zeroing) or the water trap needs emptying.
Basically put, the readings are wrong.
Last edited by ALi-B; 14 January 2010 at 07:21 PM.
#6
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The machine is not fine! Probably a blocked filter on the back of the emissions machine. The readings suggest the car is producing only oxygen and nitrogen!
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So you think you're car could produce no hydrocarbons or CO at all? A good impreza with good cat and everything in order will hit about 12-20 on HC and about 0.08-0.15 on CO with the lambda in the allowed limit.
Correct me if I'm wrong, but zero HC, zero CO and 1.02 lambda means a pass? If so I would celebrate! It could just be an extremely good cat, but I don't see it. Snapping open the throttle should take it out of close loop and drop the lambda to around 0.9 on average with CO up in the 3-4% range if you pump the throttle once a second or so.
The only time I've seen your problem is when the one or other of the charcoal filters on the back needs replacing.
Correct me if I'm wrong, but zero HC, zero CO and 1.02 lambda means a pass? If so I would celebrate! It could just be an extremely good cat, but I don't see it. Snapping open the throttle should take it out of close loop and drop the lambda to around 0.9 on average with CO up in the 3-4% range if you pump the throttle once a second or so.
The only time I've seen your problem is when the one or other of the charcoal filters on the back needs replacing.
#12
i test cars all day at work and the machine reads ok and the hc test is always calibrated before test i have posted this to see if anyone knew what would cause this i will post some pic to show
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