ACiancio Posted January 16, 2009 Report Share Posted January 16, 2009 My wife was driving our 850 home from work today and the CEL came on. when I got home I ran up to advanced to pull codes. there where 6 codes. a misfire code for all 5 cylinders. my wife said she felt no loss of power or any strange noise from the engine. my question is how does the OBD II calculate a misfire. and what could cause it to show a misfire on every cylinders without the driver noticing anything. Link to comment Share on other sites More sharing options...
volvoskiah Posted January 16, 2009 Report Share Posted January 16, 2009 My wife was driving our 850 home from work today and the CEL came on. when I got home I ran up to advanced to pull codes. there where 6 codes. a misfire code for all 5 cylinders. my wife said she felt no loss of power or any strange noise from the engine. my question is how does the OBD II calculate a misfire. and what could cause it to show a misfire on every cylinders without the driver noticing anything.are your spark plugs / cap and rotor in good condition? Link to comment Share on other sites More sharing options...
64pvolvo1800 Posted January 16, 2009 Report Share Posted January 16, 2009 My wife was driving our 850 home from work today and the CEL came on. when I got home I ran up to advanced to pull codes. there where 6 codes. a misfire code for all 5 cylinders. my wife said she felt no loss of power or any strange noise from the engine. my question is how does the OBD II calculate a misfire. and what could cause it to show a misfire on every cylinders without the driver noticing anything.Misfire on ALL, i would look for impending coil failure. Having said that, without any stumble or loss noticed it does seem weird. Double check common ignition parts such as coil wire, cap and rotor as has been suggested. I would clear them and let it ride for now. As far as your actual question....not really sure what they monitor to calculate/derive this fault. Link to comment Share on other sites More sharing options...
ACiancio Posted January 18, 2009 Author Report Share Posted January 18, 2009 Well its been 2 days and no problems, CEL hasn't come back on and the engine is strong and smooth. anybody know how the OBC II calculates a misfire? Link to comment Share on other sites More sharing options...
--Aaron-- Posted January 18, 2009 Report Share Posted January 18, 2009 I'm not sure how misfires are calculated but am curious as to how new your ignition components are? i.e. plugs, cap, rotor, wires as mentioned above Link to comment Share on other sites More sharing options...
Keaton85 Posted January 18, 2009 Report Share Posted January 18, 2009 It could have been just a flook thing, or maybe ran to low on fuel... Worry about it when the light comes back on with the same thing. Till then forget about it! Link to comment Share on other sites More sharing options...
info2x Posted January 18, 2009 Report Share Posted January 18, 2009 To my knowledge there is no OBD II requirement on how misfire is detected, only that it has to be detected. Depending on the detection algorithm a SEVERE bump could set a code. Although CARB and the EPA allow the misfire diagnostic to be disabed on rough road scenarios. Link to comment Share on other sites More sharing options...
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