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200 Series General Forum for the Volvo 240 and 260 cars |
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New MOT. Good emissions. Lambda top end of scale?Views : 843 Replies : 19Users Viewing This Thread : |
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Sep 20th, 2018, 22:51 | #11 | |
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Thanks for that. |
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Sep 20th, 2018, 22:58 | #12 | ||
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I also remember the burn off procedure. There's a revs and volt meter procedure to test that the burn off signal is sent to the air mass meter. I used that test when I was checking my air mass meter nearly two years ago. At that time I did need a new one. Quote:
And I can't get the four gas readings with DIY equipment so I'll stop thinking so much about this. . Last edited by Stephen Edwin; Sep 20th, 2018 at 23:57. Reason: Tiny little insignificant details.... |
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Sep 21st, 2018, 07:49 | #13 | |
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So I really don't understand how Volvos can never suffer from a dirty MAF sensor, as surely some contaminants will not simply burn off? But happy to take your word for it! I'm new to Volvos but, in my experience, while you will improve poor MoT emmision figures (HC and CO) by getting the engine and cat really hot, you're unlikely to make improvements to a high lambda figure by doing this. Unless of course this is another weird Volvo thing that I've yet to understand!
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Sep 21st, 2018, 08:24 | #14 |
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One of the connections on the oxygen sensor is a heating element.
It's fed from fuse 4 on my car, the same as the in-tank fuel pump. I presume if the element had failed the sensor would still work, but would be slow to heat up and lose it's heat quickly if the engine were left idling, eg at an MOT? |
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Sep 21st, 2018, 08:50 | #15 |
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Clifford, I've heard of the heating element. If I remember correctly it was introduced part way through 240 production. Was it continued for all 240s or was it phased out? Can one spot it by the number and/or colour of the wires? Would it burn off carbon or does it "only" heat up more quickly to an ordinary operating temperature?
Anyways as Clan advises burn off carbon from the front pipe and the sensor by may I say "an uphill Italian Tune Up" I shall endeavor to try that. Zebster. So far as I remember, forum experience tends towards letting the LH electronic system do what cleaning is necessary to the air mass meter. A brief spike of voltage applied automagically when the engine is switched off. . Last edited by Stephen Edwin; Sep 21st, 2018 at 09:03. |
Sep 21st, 2018, 09:12 | #16 | |
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You do still need to find the reason for the lean running.
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Sep 21st, 2018, 09:27 | #17 | |
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So far as I know, Volvo or perhaps Bosch of course provide the pulse of electricity to burn any contamination off the air mass meter wire? Yes I have "made a note" re lean running. |
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Sep 21st, 2018, 09:59 | #18 | |
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If we're ruling out the MAF sensor, then maybe you have a leak on the intake side? I'd suggest spraying brake cleaner in small bursts at any potential leakage point to see if the idle surges.
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Sep 21st, 2018, 10:13 | #19 | |
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At the moment, I was just asking about the MOT calculated Lambda in general. I'll be looking in to the lean running idea somewhat later. Life gets on top of me so I go in small steps. |
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Sep 21st, 2018, 10:44 | #20 | |
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Good luck with it.
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