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 Posted: Tue Oct 09, 2012 2:28 pm |
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Joined: Oct 08, 2012
Posts: 18
Trade Rating: 0
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hiya all,
i have an mot fail on,
exhaust emissions carbon monoxide content after 2nd fast idle
exhaust emissions lambda reading after 2nd fast idle outside specified limits.
now i have noticed it failed on the same thing last year and then passed previous owner says he fitted new cat and lambda sensor, now the main question i have is the new lambda sensor is a spliced unit i.e the cables are joined from original plug to new lambda sensor, are these any good and what would reccomendations be for cures as i am unsure about what second fast idle is.
one thing to point out is that at the time of testing the exhaust had come apart before the cat and was blowing at the joint could this affect the second fast idle????
thanks in advance guys..
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Posted: Tue Oct 09, 2012 5:44 pm |
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Joined: Feb 07, 2010
Posts: 838
Trade Rating: +2
Location: Taking a gearbox off somewhere
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Yes if the exhaust is leaking gas before or near any of the sensors then it can affect the lambda sensor readings and this can lead to MOT failure.
The connection between the lambda sensor and the plug should be ok as long as the connections are in good condition.
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Posted: Wed Oct 10, 2012 9:03 am |
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Joined: Oct 08, 2012
Posts: 18
Trade Rating: 0
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That sounds good, just worried as the sensor is before the break in the system, do you still think it could affect emmisions or should i replace lambda and repair the joint on exhaust?
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| if it aint broke, don't fix it... when it breaks, hit it with a hammer... | |
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Posted: Thu Oct 11, 2012 3:18 pm |
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Joined: Jul 30, 2012
Posts: 28
Trade Rating: 0
Location: Blackpool
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I would fix the exhaust, and take it for an Italian tune-up (rag it!) just before the retest.
But that's just me. 
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Posted: Sun Aug 11, 2013 6:04 am |
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Joined: Aug 11, 2013
Posts: 2
Trade Rating: 0
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can anyone help which lambda sensor does secund fast idle relate to, post cat or pre cat?
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Posted: Sun Aug 11, 2013 6:04 am |
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Joined: Aug 11, 2013
Posts: 2
Trade Rating: 0
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can anyone help which lambda sensor does second fast idle relate to, post cat or pre cat?
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Posted: Sun Aug 11, 2013 7:30 am |
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Joined: Aug 04, 2011
Posts: 1343
Trade Rating: 0
Location: Swindon
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Both. The reading for the MOT is taken at the tail pipe. Any defective lambda or leak will cause a fail. Fix the exhaust leak first. Was the reading high or low. It should be on your fail certificate.
High reading (excess 02) is usually an exhaust leak post lambda and often post cat.
Low reading is usually leak pre lambda.
Get all of the readings from your fail certificate and we will have a better idea what we are looking for.
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| Morris 1000, Austin 1100, Escort Mk2, Fiat Mirafiori, Alfa 33, Alfa GT Junior, Alfasud, Alfetta GTV (2x), Alfa 164 3.0 V6, Alfa 164 2.0, Alfa 75 V6, Alfa 156 2.4 (diesel remapped 200bhp), Alfa 147 GTA (3.6 295bhp), Alfa 159 (diesel remapped 245bhp 300ft.lbs @ 2500rpm)
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