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Thread: 'rough running' Cylinder 6 Thor p38 MAF?

  1. #1
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    'rough running' Cylinder 6 Thor p38 MAF?

    Hi guys,

    My nanocom is indicating that I'm getting rough running on several cylinders but its more apparent on cylinder 6. Cylinder 6 is also persistently logging misfires and throwing error codes (p0306). I'm also getting a p1319 code. I have also got various lambda sensor error codes and other misfire codes which come and go.

    The car is not audibly misfiring and seems to drive ok

    Replaced so far:

    Plugs
    leads
    coil packs

    The nanocom is also suggesting outrageous MAF readings, in the range of >24 g/s at idle. These readings rise in proportion to the engine revs.
    My understanding of engine sensors (what each does, how they interact), fuel trims etc is still somewhat limited. Does anyone have readouts of a properly running engine?

    Is it possible that a faulty MAF could effect a single cylinder? I've attached the readout of my nancom sitting in my driveway after a spin around the block.Any suggestions on what to try next?

    Cheers
    Attached Images Attached Images

  2. #2
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    It seems to me that your MAF reading is low, even for idle. I reckon your O2 sensors are looking good given your fuel trim numbers.
    I’d be replacing the MAF and doing an adaptive reset.
    2002 D2 4.6L V8 Auto SLS+2" ACE CDL Truetrac(F) Nanocom(V8 only)

  3. #3
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    Quote Originally Posted by biggin View Post
    It seems to me that your MAF reading is low, even for idle. I reckon your O2 sensors are looking good given your fuel trim numbers.
    I’d be replacing the MAF and doing an adaptive reset.
    Thanks Biggin, I had another look this morning and I think the O2 sensor for bank 2 is faulty. 1 02 sensor is fluctuating between .1 and .9 (which I understand is how they work) while 2 sits at about .4. I can't imagine that's the solution to rough running in a specific cylinder but it certainly can't be helping.

  4. #4
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    It’s true what you say about the O2 sensors operation.
    It does seem that #2 is faulty. However it is strange that both your fuel trims are close to 1.00.
    When I had problems with my sensor, trim on the bad side was around 1.40.
    Have you tried an adaptive reset? It won’t hurt.
    2002 D2 4.6L V8 Auto SLS+2" ACE CDL Truetrac(F) Nanocom(V8 only)

  5. #5
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    +1 on the adaptive values reset as a first step.
    Get some special MAF cleaner spray and give that a clean up too.
    The MAF would not affect a single cylinder, it would affect all of them.
    I would also pull the plugs and have a look, see if they are carboned up and all black, which would indicate overfuelling.
    Check both sides to make sure it's not just one bank affected.
    Let us know how that goes.
    Cheers, Pete.

  6. #6
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    So I've replaced the dodgy O2 Sensor and reset the adaptive fuel values. The following has happened.

    It is still 'running rough' on several cylinders but particularly Cylinder 6.
    It is no longer clocking up 'misfires' at an alarming rate but still logs one or two.

    HOWEVER

    The voltage for the new 02 sensor seems to have remained at approx .45 rather than fluctuating like the other. I am also still getting lambda sensor faults for the replaced 02 sensor. (p1000 and p0155)

    Pulled the sparkplugs and nothing seems too weird there.

    I have not yet done anything with the MAF so will try cleaning that next. Could I draw attention to the readings I'm getting from the MAF in the original post. The Nanoncom reads in g/s right? As i understand a correct idle reading should be about 6 g/s and mine is reading 20 g/s? Has anyone experienced weirdness with the units the nanocom measures in? It would seem my readings would make sense at kg/h rather than g/s

  7. #7
    4X4V8 Guest
    I have just driven my Thor P38 1/2hr and plugged in the Nanocom.
    (I have have random misfires cyl 1, less than silken idle and I thought I noticed an increase in fuel consumption last long run recently.

    My Nanocom doesn't show 'g/s' in the readout like yours does - does your Nanocom have the latest update?
    It's a bit confusing because I just checked Blackbox Solutions and it says the MAF reading is in kg/h. My Nanocom just says 'MAF Sensor' and the reading.

    My MAF at '27' is reading similar to yours. From the little I've read, this should be more like '20'.

    Most other outputs are also similar to yours. Some are a bit out, still researching. No fault codes present though.

    I've tried to post pics from the Nanocom but having problems uploading. Will try again later.

    Sorry I'm not of much help here....

  8. #8
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    Quote Originally Posted by 4X4V8 View Post
    I have just driven my Thor P38 1/2hr and plugged in the Nanocom.
    (I have have random misfires cyl 1, less than silken idle and I thought I noticed an increase in fuel consumption last long run recently.

    My Nanocom doesn't show 'g/s' in the readout like yours does - does your Nanocom have the latest update?
    It's a bit confusing because I just checked Blackbox Solutions and it says the MAF reading is in kg/h. My Nanocom just says 'MAF Sensor' and the reading.

    My MAF at '27' is reading similar to yours. From the little I've read, this should be more like '20'.

    Most other outputs are also similar to yours. Some are a bit out, still researching. No fault codes present though.

    I've tried to post pics from the Nanocom but having problems uploading. Will try again later.

    Sorry I'm not of much help here....

    Thanks so much for that! That is excellent information. Sorry you’re having similar problems. I’ve got my car booked into get ball joints done in a couple of weeks time so I’ll ask the mechanic if he has any thoughts.

  9. #9
    4X4V8 Guest
    Here are my Nanocom readings. I was waiting for my wife at the shops so taken in a bit of a hurry. Idling in Park with a/c on. Not very scientific sorry, but at least some indication.

    From my reading last night both your and my MAF readings are too high (assuming that they are both in kg/h as Blackbox Solutions website suggest they are, with latest software update I presume, which I think my Nanocom has; but your reading suggests grams/sec).
    Idle trim at around 1.48 seems too high also but I need to check that's actually the case.

    IMG_5216.jpgIMG_5217.jpgIMG_5218.jpgIMG_5219.jpgIMG_5220.jpgIMG_5221.jpgIMG_5222.jpgIMG_5223.jpg

  10. #10
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    Did you use genuine a Bosch sensor, or aftermarket?
    I found out the hard way with my thor engine, aftermarket caused all sorts of weird problems, as soon as I replaced those with genuine Bosch and did an adaptive values reset, all came good instantly.
    If it were me, I would replace both O2 sensors at the same time, at least that way you know they are both good and starting from a good base point.
    Definitely give the MAF a clean, only use a special MAF spray for that, don't use carcy cleaner or something like that.

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