Random idle misfiring and strange fuel trims. DS3 THP
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Thread: Random idle misfiring and strange fuel trims. DS3 THP

  1. #1
    X8R
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    Default Random idle misfiring and strange fuel trims. DS3 THP

    Hi all

    I recently bought a 2011 built Citroen DS3 1.6 THP that had a myriad of issues, now mostly solved. An intermitent misfire at idle (cold and warm) still remains as well as some mid-range hesitation and lack of torque. It feels like it is retarding ignition or pinging. Strangely, there are no fault codes or check engine light on.

    Originally with 86,000 km it was running very rough. I got following operations done at my local BMW mini specialist in Burwood, Melbourne which made the car run a lot better:
    - Walnut blast intake valves ($450)
    - Changed one bad coil
    - Replaced all 4 spark plugs

    At 89,000 km, Citroen changed the timing chain and tensioner and advised the intake valves were "very dirty" and quoted the exorbitant sum of $2000(!) to clean them which I didn't end up doing. Can the valves be so dirty only after 5,000 km of a walnut blast? I do use Castrol EDGE 5W-40 A3/B4 the manual calls for. I did a complete oil flush and oil filter change at 90,000 km myself.

    - My crappy OBD reader can't count the misfires but I can definitely hear my exhaust puffing randomly and shaking at idle. Torque at mid range seems lacking. Surges and hesitates at wide open throttle (WOT) below 4,000 rpm
    - I checked the fuel pressure and I get a very constant 5000 kPa at idle to ~11000 kPa at WOT so I don't think my HPFP has failed yet. Cold and warm values are the same even when misfiring.
    - My short term fuel trims do look very strange. At idle, the trim is mainly constant around 0% change even when shaking. At light load the fuel trim fluctuates up to +15% while at WOT can go up to -15%. To be honest, these values don't make much sense to me. Unfortunately, my OBD reader for some reason can't read the long term fuel trims which might tell more.

    - I checked for evident vacuum leaks or broken hoses but I can't see any
    - I see there's quite a lot of vacuum inside the valve cover. I can't even take the oil filler cap off at idle
    - The brittle PCV hose on the driver side seems in good condition and if disconnected, the idle gets even worse as it should. It is very oily inside. My car burns around 1 litre every 5000 km
    - The passenger side PCV rubber hose going to the turbo is very clean and there's no oil residue at all. Is looks like it might be blocked or stuck closed?

    Due to the intermitent nature of the bad idle and hesitations under load, my guesses are:
    - Bad O2 sensor?
    - Spark plug gap too big? I am running the stock 0,75mm
    - PCV valves stuck open / closed?
    - Am I missing anything? How can I diagnose the above?

    Thanks in advance, I've spent a few weeks researching in this forum as well as all the R56 mini forums out there. This car is driving me crazy, it should be more powerful than it is and the intermittent rough idling is annoying. Unfortunately, the mechanics I have visited so far have not been able to make it run right. I iz sad.

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    Is there anyone in Melbourne with a THP engine willing to catch up over over a beer or two?
    Last edited by X8R; 19th December 2018 at 04:28 PM.

  2. #2
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    The behaviour without error codes suggests carboned inlet valves/ports, or plugs or coils. All of them done, though how did someone say the valves needed work without dropping the manifold?

    A regular miss should produce an error, and swapping a bad coil should make the code number swap.



    Trims might be a timing problem. Oily could be leaking at the turbo seals.

    5-40 is a bit thickish. Current advice is C2 0-30W, that is the same as the PSA diesels. This is to minimise ashing the ports.

    It needs more thought, by me at least, but some codes would help. DS3s should accelerate very smartly and smoothly.
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    Firstly, have you had the airbag recall performed?

    Is the battery in good shape? The car isn't tolerant of a weak battery. Load test it.

    Check with a dealer for any outstanding service campaigns. There are a couple that may be relevant to your car, such as the oil solenoid and coolant temp sensor.

    From what you mention, it may want an engine/cam cover as that has two diaphragms in it for the PCV and they do fail. The larger one is under a round cover and you can buy a replacement, but that won't help you if the smaller diaphragm inside has failed too.

    Did you read this? Peugeot 308 EP6 1.6 THP revised valve cover design?

    PSA now suggest using the low ash oil they specify for the HDi particle filter cars. This is meant to reduce the valve deposits. It's likely a good idea to use a cylinder head cleaner like the Subaru foaming product with each oil change.

    Plugs won't make it much past 40K. Coil faults are sometimes phantom and the suggestion now is to swap them around and see if the fault moves the coil before concluding a coil is faulty.
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    1000+ Posts dmccurtayne's Avatar
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    If itís hard to pull the oil cap off while running replace the rocker cover donít bother with the kits by the time you get it apart and find itís all stuffed you are better off doing it all also they donít last long at all


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    X8R
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    Quote Originally Posted by seasink View Post
    The behaviour without error codes suggests carboned inlet valves/ports, or plugs or coils. All of them done, though how did someone say the valves needed work without dropping the manifold?

    Trims might be a timing problem. Oily could be leaking at the turbo seals.

    5-40 is a bit thickish. Current advice is C2 0-30W, that is the same as the PSA diesels. This is to minimise ashing the ports.
    I am not sure the dealership had a look at the actual ports to see the valves. I really doubt they were bad after a walnut blast (5,000km ago and some Liqui Moly intake decarb done 1,000 km before. I did another extra spray decarb before my last oil change.

    The dealership changed the timing chain and the behaviour was exactly the same so I don't expect to be a timing issue.

    Thanks for the advice on the oil. I see now everyone is running low-mid SAPS and thinner oil. Is there any particular brand you guys recommend? I thought my behaviour could also be due to low speed preignition (LSPI) caused by the oil.

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    X8R
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    Quote Originally Posted by David S View Post
    Firstly, have you had the airbag recall performed?

    Is the battery in good shape? The car isn't tolerant of a weak battery. Load test it.

    Check with a dealer for any outstanding service campaigns. There are a couple that may be relevant to your car, such as the oil solenoid and coolant temp sensor.

    From what you mention, it may want an engine/cam cover as that has two diaphragms in it for the PCV and they do fail. The larger one is under a round cover and you can buy a replacement, but that won't help you if the smaller diaphragm inside has failed too.

    Did you read this? Peugeot 308 EP6 1.6 THP revised valve cover design?

    PSA now suggest using the low ash oil they specify for the HDi particle filter cars. This is meant to reduce the valve deposits. It's likely a good idea to use a cylinder head cleaner like the Subaru foaming product with each oil change.

    Plugs won't make it much past 40K. Coil faults are sometimes phantom and the suggestion now is to swap them around and see if the fault moves the coil before concluding a coil is faulty.
    Hi David

    Yes, airbag recalled as well as all the service campaigns, I called a couple of weeks ago to make sure all was done. Cheers.
    I also changed the battery recently, the car was running like crap with an old one!

    I also suspect the cam cover and it's PCV's may have failed. The amount of vacuum in is tremendous. The car is adding fuel +15 to 20% (STFT) at low loads as there was a vacuum leak. At WOT it takes about -10% fuel off. Thanks for the thread, I'll have a proper read on lunch time.

    I may buy 4 new coils just to be on the safe side and get some C2 oil for the next oil change.

    Thanks again for the input, you guys are legends!

  7. #7
    X8R
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    Quote Originally Posted by dmccurtayne View Post
    If it’s hard to pull the oil cap off while running replace the rocker cover don’t bother with the kits by the time you get it apart and find it’s all stuffed you are better off doing it all also they don’t last long at all
    Definitely, I think this is the main culprit.
    https://www.ebay.com.au/itm/Citroen-...PyOK:rk:5:pf:0
    For $190, I think it should be an easy fix.

    Thanks a lot for your opinion!
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    Citroen always recommend Total Quartz Ineo ECS 0-30w (when the car was new it was 5-30W, but they have revised the recommendation)

    In some states it is hard to get, but in Vic the Total distributors would sell you 3 off x 5L containers per carton at a sensible price. Slightly more ash content, but available everywhere is Penrite Enviro+ C2

    I suspect the dealership took a stab at diagnosis on the basis of the driving behaviour as I did. The vacuum holding the cap is a bit off - dmmccurtayne knows these engines.

    My DS3 got its valves and ports cleaned with solvent and skinny scrapers using a mirror to see by. It was an all day job. PSA dealers stock the rather expensive solvent. I am very fond of the little car.
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    Re valve cover - note differences in the referred thread. Get seals as well (inc at plugs).
    Screenshot-2.jpg

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    X8R
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    Thanks for the recommendations!

    *** UPDATE ***

    I finally got the OBD working well and it is showing some misfires in cylinder 1 and 3. I swapped the coils 1 to 2 and 3 to 4. And the misfires did not travel with the coils. I suspect the misfires are not coil related then and may be carbon buildup or compression leak?

    Maybe the next job will be to remove spark plugs and recheck gaps and condition.

    If everything else seems right, I'll continue with some compression or leak tests. It not sure now if a bad valve cover/pcv can cause this cyl 1 and 3 misfire only. Cil 2 and 4 show 0 misfires at all.
    Strangely, the misfires are not constant, sometimes they don't happen at all during a drive cycle...
    Last edited by X8R; 24th December 2018 at 12:57 PM.

  11. #11
    1000+ Posts dmccurtayne's Avatar
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    If youíve got incorrect vacuum then your fuel trims will compensate up to the limit then you get random misfires but in saying your getting 1 and 3 that smells like a fuel pump to me but the rocker cover still will need doing lesser of two evils


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    Hi I have read your thread if you have misfire faults on 2 cylinders I would say itís the hp pump, you also mentioned that the car can misfire from cold which is another sign the pump is failing. As for the rocker cover if the Pcv has failed they often make I whistling sound at idle.

  13. #13
    X8R
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    Hi dmccurtaine and turbo pug

    The HPFP could be one of the suspects too but I am getting constant pressure at idle and spikes and stays up consistently under boost. Excuse my ignorance but does the fuel pump have different outlets for different cylinders? Isn't there a common rail? I'd guess if it was a HPFP issue, all cylinders would randomly misfire, not only 1 and 3?

    I leave the screenshots of the misfires in cyl 1 and 3
    Screenshot_20181222-155245_inCarDoc Pro.jpg
    Screenshot_20181222-155254_inCarDoc Pro.jpg
    Screenshot_20181222-155300_inCarDoc Pro.jpg

    Plus the -strange to me- fuel trims under idle (left of the graph) and at 2500 rpm no load (right of the graph)
    Screenshot_20181222-155616_inCarDoc Pro.jpg

    Don't you think the ECU is trying to compensate too much? I'd guess I have a vacuum leak or PCV valves don't work properly but I don't hear any hissing noises.

    Thanks for your comments!
    Last edited by X8R; 14th January 2019 at 03:18 PM.

  14. #14
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    The have two pistons that surge in volume around injection time thins is why the pumps have this problem , if that makes sense.
    The new ep6 pumps are just single piston but not interchangeable


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  15. #15
    1000+ Posts dmccurtayne's Avatar
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    Do you have any live fuel trim data at idle and 2000rpm


    Garage C5 X7 3008 XTE
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    X8R
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    Quote Originally Posted by dmccurtayne View Post
    Do you have any live fuel trim data at idle and 2000rpm


    Garage C5 X7 3008 XTE
    Gone but not forgotten 206 GTI 180 306 XR SED 405 MI16 x2 xzara VTS 406 SV 206 XT Berlingo 2011 (best car ever) 306 HDI 307 XSE HDI touring
    Fix it right the first time
    Hi dmccurtayne, yes, it's the last photo in y last post. Screenshot_20181222-155616_inCarDoc Pro.jpg The left side of the graph is at idle, and the right side is at 2500 rpm (no load). I find the ecu is trying to overcompensate too much. What's your opinion?

    Cheers
    Oscar
    Last edited by X8R; 14th January 2019 at 03:18 PM.

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