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Excess Exhaust Soot (THP Petrol)

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  • Excess Exhaust Soot (THP Petrol)

    Hi from down under, tried searching all over the net and the forum before posting and hoping somebody can shed light on my excess soot issue.

    I have a 2011 (build Dec 2010) DS3 THP with around 120,000km (75k miles) and have owned it since the back end of 2015. Shame they didn't import the oil burner to Aus, we had one in the UK before we emigrated over here.

    I have the typical love hate relationship with it (I love it, it hates me ) and seem to be constantly spanner fettling to keep it happy.. Above the usual servicing :

    - Walnut blast every 20-30k - so 3 times since I bought it surprising how quickly it builds up.
    - Replaced HPFP
    - Replaced stretched timing chain and all the associated gubbins
    - Replaced thermostat

    Anyway on to my latest issue and I'm hoping the brains trust on here can help.

    Over the last few months the level of soot on the exhaust tips has become excessive, here's my observations and thoughts but your input would be welcome :

    Car as always been serviced every 10k
    I'm running it on 95RON e10, handbook implies this should be ok
    Good compression across all 4 cylinders
    There's no fault codes
    Power is good with no issues other than the occasional misfire when accelerating in a high gear from a lowish speed, I believe this is common.
    Some minor oil consumption, more evidenced when the motor has been idling 10-15 mins and a puff of blue smoke when pulling away. Some minor play in the turbo spindle but not excessive.
    I am getting some oil mist coming from the cam cover during running but it's not to bad.
    Under hard acceleration there is some black smoke coming from the exhaust at high revs.
    Plugs are clean and gapped to spec, coil packs are <30k old

    I'm wondering :

    1) Could it be the the cam timing (planning on checking soon - not a fun job) has slipped ?
    2) Leaky injectors ?

    Your thoughts ?

  • #2
    IMO 95 RON isn't what the engine likes best, maybe run a cleaner through (BGK44?) try RON 98/99 for a while
    It sounds like some sort of fuelling issue- running rich?

    Sounds like an engine that's older than its mileage, although at 2010 model its a very early one

    Have you had it tuned?
    Jog on Noddy


    • #3
      Thanks for the feedback Chris_Blue, fuel 'choice' and running rich was starting to play on my mind, I checked fuel trims the other day and LTFT was around 6% which is above what I expected and higher than it was before I switched to E10. I assume it's down to the ethanol content of the fuel, lower calorific value and it's trimmed up as a consequence - hence the soot. Strange though as fuel econmony is good at 5.8l/100kmm (40.55mpg) over the last 6000km (3800 miles)0, predominatly motorway driving with the occasional spirited A road blast.

      I'll run the old girl down to fumes and start with a fresh tank of 98 from a known brand and run through some fuel system cleaner. I may struggle to find BG44K out here as it doesn't appear generally available.

      The motor is the original as I contacted the only owner after purchase, he had it independent serviced after the initial service and I have been doing it ever since, having served my time on the spanners many years ago I prefer to maintain my own vehicles. It is a very early one and having researched to distraction these motors suspect I bought one with all the early foibles.

      It is untuned, if I could find somebody out here that is able to properly do it that would likely change though.

      It did have an ECU update at the end of last year when I took it back for the airbag recall and the dealer told me it was subject to a campaign, not sure what was updated as they did not share the detail.

      I have a few days off next week so plan on going through a few things; checking the cam timing (if I can find the digital inclinometer), operation of the VVT solenoid and changing the plugs.

      I last walnut blasted less than 10k ago so won't bother with that. I've found I start getting frequent misfire CELs when it's ready for this procedure.