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Thread: 453 engine problem

  1. #1
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    453 engine problem

    My sep 2015 0.9 turbo 453 has developed a weird problem .....

    It drives fine, you wouldnít know there was a problem until you come a stop and let the engine idle !

    Although the Rev counter just shows a steady 1k (ish), the engine appears to be hunting (it feels lumpy in the drivers seat) or maybe itís a misfire ?

    But as mentioned it drives perfectly, normal power levels smooth etc - until you let it idle.

    Two other points of note, it has a full merc service history , 4 services in 4 years and just 40k miles. NO engine light has come up.

    Also only once or twice Iíve been to the shops , left it for a half hour or an hour, and when you come to restarting it takes a bit longer to fire up, probably 6 or 7 full revolutions. This has only happened a couple of times max though, in the past couple of months.
    The hunting has only just started in the past week or so.

    Itís still on the original plugs though, but I would have thought if it was plugs/HT related it would be a bit chuggy as you accelerated too? (it isnít)

    To further complicate matters I thought mebbe itís the crank sensor, .... but on this engine thereís a crank sensor AND a camshaft sensor !! Why would it have a camshaft sensor too ? And could that be the problem rather than the crank sensor ?.

    Any ideas ?

    Or should I just take it to Merc for a possible spanking ?
    Last edited by reinaldo_is_spam; 09-01-2020 at 07:13 PM.
    You're so money supermarket and you don't even know it!

  2. #2
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    On the day I decided to take it to merc , it developed a random but persistent "emergency brake assist inoperative" message too, which just pushed me even more into taking it to merc.
    They had serviced it 3 months ago - which is why I chose that route.


    It turned out to be a dodgy camshaft sensor, this fixed both faults. Apparently due to the rough idle it couldnít build up enough brake servo vacuum, hence the extra error message.

    To cap it off the merc garage wangled it under warranty/goodwill - despite it being 4.5 years old

    Result I say
    You're so money supermarket and you don't even know it!

  3. #3
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    Quote Originally Posted by reinaldo_is_spam View Post
    Why would it have a camshaft sensor too ?
    Because TDC for firing cannot simply be ascertained from the CPS unless using the trickery of monitoring variations in cranking speed - as the earlier triples did. Not sure if others use that method (Renault don't obviously) or if it even works when there are more than three cylinders.
    Good you've got it sorted - I'd never have guessed cam sensor.

  4. #4
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    Quote Originally Posted by pinger View Post
    Because TDC for firing cannot simply be ascertained from the CPS unless using the trickery of monitoring variations in cranking speed - as the earlier triples did. Not sure if others use that method (Renault don't obviously) or if it even works when there are more than three cylinders.
    Good you've got it sorted - I'd never have guessed cam sensor.
    I guess it makes timing way more accurate or defined with a camshaft sensor.

    But with very similar fault symptoms it makes choosing which one (without diags) a bit of a lottery.


    I got to play with the electric 453 smart for a few days, although with a range (on screen) of 65 fully charged, it wasn't useful for my needs over the weekend.....so I resorted to a train.

    As mentioned when fully charged it showed 65 miles range (not the 99 advertised - I guess you might achieve that with conservative driving) , but put the cabin heater/aircon on full for instance and it instantly drops to 45 onscreen !!

    The headlights didn't show any hit at all , although these maybe powered via a conventional 12V battery rather than derived from the HV battery pack.
    It did show re-gen recharging on the dash 'clock' when braking, obviously flipping the main motor over to alternator mode momentarily. (and providing an effective retardation of the car in motor braking effect.)

    BUT the range is just ridiculous. (in a bad way) - it might be ok for city use, but you'd still be plugging it in all the time.

    Double the range (or more please) and it might be more interesting... but as it stands .... naw
    You're so money supermarket and you don't even know it!

  5. #5
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    Cam shaft sensor only tells ECU where engine is in firing order. Injection timing is via flywheel rotation sensor.
    Drives a Smart Cdi - 65 to 85 MPG

  6. #6
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    Glad you got to the root of your problem, plus we all like a freebee!

    (Yippee the site actually let me post a reply again! About time!!)
    Last edited by Mr T; 17-01-2020 at 05:58 PM.

  7. #7
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    Quote Originally Posted by reinaldo_is_spam View Post
    I guess it makes timing way more accurate or defined with a camshaft sensor.
    The ECU needs to know which stroke any given piston is on to correctly time the spark and injection events, i.e. if the piston is approaching TDC is it on the exhaust stroke or the compression stroke? Without resorting to analysing crankshaft acceleration (as the first generation ECUs did) then you can't get this info from the crank sensor alone.

    With a four cylinder engine you can use a "wasted spark" method which means firing the plugs on two paired cylinders (1 and 4, 2 and 3) at once, one will be on the exhaust stroke (so the spark will be 'wasted' as it does nothing) and the other will be on compression. Injection can not be fully sequential with this system, and it cannot be used at all on a three cylinder engine as the crank pins are spaced at 120 degrees rather than 180, so no pistons move up and down together.

    My wife has the 0.9 turbo engine in her Dacia Logan so it's useful to know about this potential fault, thanks.

  8. #8
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    Quote Originally Posted by mikerj View Post
    The ECU needs to know which stroke any given piston is on to correctly time the spark and injection events, i.e. if the piston is approaching TDC is it on the exhaust stroke or the compression stroke? Without resorting to analysing crankshaft acceleration (as the first generation ECUs did) then you can't get this info from the crank sensor alone.

    With a four cylinder engine you can use a "wasted spark" method which means firing the plugs on two paired cylinders (1 and 4, 2 and 3) at once, one will be on the exhaust stroke (so the spark will be 'wasted' as it does nothing) and the other will be on compression. Injection can not be fully sequential with this system, and it cannot be used at all on a three cylinder engine as the crank pins are spaced at 120 degrees rather than 180, so no pistons move up and down together.

    My wife has the 0.9 turbo engine in her Dacia Logan so it's useful to know about this potential fault, thanks.
    Good point re four cylinder motors.

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