Toyota RAV-4 (1994 - 2000) - 96 2.0 MoT Emissions failure - strange results?

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Wed 13 May 2009 10:32
96 2.0 MoT Emissions failure - strange results? - OldSock
SWMBO's RAV4 failed its MoT test on exhaust emissions. Print-out reads:

Fast Idle Test:

CO: max 0.300% 0.000 PASS
HC: max 200ppm 0 PASS
Lambda: 0.970 - 1.030 1.091 FAIL

Second Fast Idle Test:

CO: max 0.300% 3.093 FAIL
HC: max 200ppm 90 PASS
Lambda: 0.970 - 1.030 0.922 FAIL


Natural Idle Test:

CO: max 0.500% 3.197 FAIL


I'm a bit confused by the first fast idle test. The '0' result for both CO and HC implies a remarkably clean exhaust, though the lambda figure does imply that the engine is running lean, so perhaps a low CO reading would be expected.

I gather that the second fast idle test is only performed to give the car a 'second chance' - so why are the figures so vastly different? In particular, the lambda value now indicates a rich mixture - which might explain the high CO figure. But why should the repeat test be so vastly different to the first??




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Wed 13 May 2009 11:11
96 2.0 MoT Emissions failure - strange results? - Woodspeed
Looks like a near miss! Worth doing a quick service, plugs, air filter, oil and oil filter, and give it an "Italian tune up" to clear out any crud etc, and try again. Make sure the car is HOT HOT HOT when they do the test, and not sat on the forecourt waiting MOT for an hour and the operator does not bring it up to temperature.
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Wed 13 May 2009 12:02
96 2.0 MoT Emissions failure - strange results? - bell boy
co low
hydrocarbons low
02 high
exhaust leak AFTER the cat
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Wed 13 May 2009 12:34
96 2.0 MoT Emissions failure - strange results? - OldSock
Hi BB,

That's a possibility - I'll block the tailpipe with a rag tonight and see if starts blowing a raspberry!

I still don't understand why the two fast idle tests are so different. I wasn't present at the testing, so can't say whether the car was fully up to temp or not.

A new air filter is on order - the old one was a bit, ahem, 'obscured', though only about a year old....
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