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Power loss then power back again

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  • #16
    As soon as the idle speed settles down after cold start the wastegate should close (if you are outside the car a slight whirr can be heard as the turbo starts to spin up). Not controlled by SAM in footwell though - MEG in engine compartment. Aux air pump maybe from SAM but can't remember mine clicking on start up. Only clicking from there is rear wiper relay.

    I think, the power output is on the V5 doc. Unless it's an early model Pure,(or Brabus) it should be the 45kw (circa 60hp) motor you have. Early lower power (50hp) Pures were controlled differently ie, no cycle valve.
    If you cant find your power output from the above, I might have data that will provide info from engine number.

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    • #17
      It happened again today... 60mph in 6th all of a sudden felt underpowered and slowing down and rough feeling (like a flat tyre or unbalanced wheel) or missfire. Told me to kick down to 5th and it felt smoother at over 3,000rpm. Changed back to 6th and rough feeling again at 2500 rpm.

      Going to change the plugs on the weekend.

      How many coils does the smart use? Is it just one coil box or 6 individual coils?

      5 mins of the journey it seemed fine, 5mins rough then 10 mins fine.

      Then the 20 minute journey home was fine

      Thanks

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      • #18
        Mysterious problem you have.....
        Three double ended coils. Be sure to use the plug cap removal tool and check the leads for damage in case they've just been tugged off in the past.

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        • #19
          Might be worth checking earth leads in engine bay. They aren't very substantial to begin with and can corrode.

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          • #20
            If you have a copy of Delphi DS150E you'll be able to scan for codes, any misfires are logged

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            • #21
              Changed the plugs but still the same...

              Makes a t t t t t t t t t noise at 2500rpm and above in any gear when the problem is there untill it clears

              Also when the accelerator pedal is released the t t t t tt t t t noise instantly stops apply throttle and its back again untill the problem seems to sort itself after a while...

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              • #22
                Just because it's a cheap thing to do - Put a bottle of injector cleaner in the petrol tank, It may help or it might not appear to do anything, but it certainly can't hurt!

                John

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                • #23
                  Thanks, migght give that a go but noticed I have Got a nice crack in the manifold could this be the cause?

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                  • #24
                    Slightly cracked exhaust manifolds give rise to erratic idling apparently. I'd guess your problems could be down to the same - especially if the crack is worse than slight. The noise is probably a clue.

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                    • #25
                      Trying to upload a image but the forum keeps giving me errors when trying to upload will try link to a image

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                      • #26
                        Image worked :-) thats one visible crack that I can see but also where the manifold joins the engine looks sooty... On idle i can feel the gasses escaping the crack

                        Mercedes only supply the complete turbo and manifold at over 400 but saw some on ebay as just the manifold for 120 from Germany has anyone tried these?

                        Could this be the problem?

                        Thanks

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                        • #27
                          The actuator arm looks sooty - like a substantial leak. Suspect it's cracked internally at the wastegate valve also where leaking would lose boost. Probably the cause of your problems, and likely you won't know for sure until it's replaced.
                          No knowledge of German manifolds but if new, can't see a problem in shifting your turbo cartridge into one. The Mercedes price isn't as bad as I remember - not me paying it though!
                          Leak at the head is probably a broken stud (quite common).

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                          • #28
                            Thats what I was thinking sitting at 2500rpm heating manifold up, expanding crack, boost loss and lambda sensors getting wrong readings then slowing down for town driving and traffic lights cools manifold enough for cracks to shrink then drives normal again untill the crack expands again

                            It looks like the turbo is just held onto the manifold with a clamp im guessing the actuator arm is just held on with a clip?

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                            • #29
                              A mixture of lost boost due to leaks and Lambda sensors queering the rest (it seems a leaking exhaust will draw air and confuse the Lambda sensors) sounds plausible. It'll need fixing for MOT anyway so I guess it's bite that bullet time.
                              Actuator arm is held by E-clip (circlip) and turbo to manifold by clamp - as you surmise. Be prepared to replace the turbo oil and coolant pipes as they are corrosion prone and may not survive being disturbed. You may have to remove OS driveshaft for access to them which requires partial suspension stripdown. Don't forget the possibility of broken stud(s) at manifold face where it joins to head. You will be breaking into the coolant circuit - expect fluid loss and top up. (There is a drain plug on the rear of the block, if you can catch coolant cleanly then re-useable. Bleeding will be required when done - via temp sensor at thermostat).

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