exhaust smoke

Discussion in 'The Beginner' started by paul18, Aug 2, 2015.

  1. paul18

    paul18 Funster

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    My 04 Fiat 2.3 (34k miles) sometimes has grey exhaust smoke, typically after driving a few miles and stopping at junction or traffic lights. I have been putting it down to diesel smoke, but would welcome any observations please. No other symptoms, loss of oil or power for example
     
  2. Flamenca

    Flamenca Funster Life Member

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    Diesel 'smoke' is usually black. I had puffs of black smoke when pulling away and on steep inclines. I added turbo cleaner and injector cleaner additives to the fuel and the exhaust is now much cleaner. Recently passed the MOT emission test without any problem. I do not know the cause of grey smoke but no doubt other Funsters will be able to advise.
     
  3. Derbyshire wanderer

    Derbyshire wanderer Funster Life Member

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    The grey smoke if light grey could actually be steam from either condensate or rainwater that drips down the exhaust. This should stop after a good run when everything is at working temperature.
    Assuming your oil and coolant levels are always good, you should not be too concerned.
    A possibility will be a leaking injector that causes incomplete combustion and a little smoke. This happens when you slow down on overrun with the accelerator at rest. This would benefit by treating the fuel with a good quality fuel and injector cleaner which hopefully will sort it.
     
  4. Bobby22

    Bobby22 Funster

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    Last edited: Aug 2, 2015
  5. paul18

    paul18 Funster

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    Sounds more like this.
     
  6. paul18

    paul18 Funster

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    Well, we have completed a thoroughly enjoyable 720 mile 15 night tour of Brecons, Peak and Lake district, North Yorks moors and ending up in Stratford upon Avon. Put required dose of Redex diesel treatment in, seems to have had little or no effect, but 720 miles were otherwise mechanically uneventful, including a 4 hour stop start slog down M5. Should I worry, or leave it till Mot and service in November? We have a long weekend end of Aug anda week away in October planned. Any advice kind people?
     
  7. Badknee

    Badknee Funster

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    As has been said, steam from start up can take ages to clear. Fuel has a lot of water in it and 99% of exhaust corrosion is from the inside!
    Black smoke on acceleration is normalish but shouldn't be too bad ( oil/ air filter change) grey 'smoke' is probably blue'ish grey and is un burnt fuel most of the time. If the engine is hot and it has been stood idling say in traffic it could be valve stem seals leaking of piston rings but at 34k I wouldn't think it's that.
     
  8. paul18

    paul18 Funster

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    Bluish grey, on run down as described earlier, or when idling, then moving forward and idling again (typically) but not always or persistent. Can be excessive if reversing hard, say up sloped pitch? Its not steam from start up and never black.
     
  9. TheCaller

    TheCaller Funster

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    I'm no expert on modern diesels, so don't put much reliance on this, but bluish-grey smoke after idling on an 04 engine that has only done 34k miles sounds like an engine suffering from having done too little work.

    Are you fairly light on the throttle?
     
  10. Derbyshire wanderer

    Derbyshire wanderer Funster Life Member

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    If the oil and water levels have defiantly not gone down, the only thing left is injector leakage.
    Required dose of Redex? I assume you have treated a tankful but this is unlikely to be enough to shift the issue if at all in such a short time. Look for a fuel treatment that is designed to be put directly in the fuel filter so it gets used as a concentrate (pig of a job on Fiat filters though).
    You still may be needing a diesel specialist to sort a dodgy injector if the nozzle is faulty. This can be sheer bad luck and nothing to do with how you look after it. Fuel treatments will never sort is mechanical fault unless it is a blockage issue and tbh a blockage would more likely cause smoke all the time.
    If you do end up looking at using a specialist, take lots of advise to make sure you are totally happy with where to go. This is one area of the motor trade that can eat good money and get nowhere fast. It is worth travelling to get the right result. You could of course remove them and post but they would be better off seeing the problem first hand.
    The only other thing I can think of is to check that the throttle is defiantly closed on overrun otherwise fuel will still be injected ( should be fly by wire so will need a diagnostic connection to check).
    As always, it is very difficult to be precise when diagnosing on descriptions alone so please bear this in mind with the advise.
     
  11. paul18

    paul18 Funster

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    Thats a very comprehensive answer, thank you. My van is due its MOT in October, so I will probably wait as we only have two more trips planned, maybe three, and they are relatively close. I am assuming if there is an injector issue, it will be picked up on the emissions test?
     
  12. Derbyshire wanderer

    Derbyshire wanderer Funster Life Member

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    Not likely to be a problem to the mot tester as they are only concerned with 'excessive smoke'. If it was bad enough to fail a mot, you would have probably had a tug by plod during your recent travels.
    If it is too much for you to put up with, you will have to decide what to do.
    My last van did a similar thing but was always in slow traffic. Quite embarrassing sometimes when the other drivers were staring as if it was polluting society but I never did bother to sort it.
     
  13. paul18

    paul18 Funster

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    Its never really bad enough to get pulled over
     
  14. Frentchy

    Frentchy Funster

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    Just a thought, but I had the same light gray smoke on our Boxer van and lived with it for ages till it slowly got worse and began to run lumpy on high revs, found that a slight air intake leak on diesel filter inlet joint was the cause, try running the engine at high revs for 30 odd secs,to see if it gets worse.
     
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