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Thread: V6 CDTi - component questions.

  1. #1
    Regular Member gtr1000's Avatar
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    Vehicle : Insignia

    Trim : Sri

    Engine : 140 Ecoflex S/S

    Year : 2013

    Default V6 CDTi - component questions.

    Just trying to get my head round the various issues that have arisen or may arise with my 46k miles 54 plate Y30DT:

    1) SCVs - do they merely block up or fail/break? Why do they block up or why do they break?

    2) Injectors - do they gum up or fail/break? Same as above, either answer, why?

    3) EGR - does it block up or break? Same as above, either answer, why?

    4) MAP sensor - not familiar with this so don't know what to expect .

    Hopefully the answers from you gurus might help me and others.

    Oh, still haven't heard from admin about our sub forum.

  2. #2
    Regular Member m8internet's Avatar
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    Quote Originally Posted by gtr1000 View Post
    1) SCVs - do they merely block up or fail/break? Why do they block up or why do they break?
    You might want to read up on Suction Control Valves
    They determine the amount of fuel to be supplied to the injector
    They normally block up if debris passes the fuel filter
    As a result it acts as a last defence before the engine, to prevent permanent damage

    Quote Originally Posted by gtr1000 View Post
    2) Injectors - do they gum up or fail/break? Same as above, either answer, why?
    Fuel passes through them and eventually the detonation in the combustion chamber damages them
    If one has been damaged and needs replacing it is prudent to replace them all, as the others will be in similar condition

    Quote Originally Posted by gtr1000 View Post
    3) EGR - does it block up or break? Same as above, either answer, why?
    Correct term is EGR valve
    Diesel engines basically don't need them
    They are fitted in order to meet EU requirements over emissions
    As the hot exhaust gasses pass through them the valve wears out, the same issue applies to both petrol and diesel
    It is usually worse in vehicles used on short trips where the engine rarely gets up to full temperature, resulting in soot collection within the valve

    Quote Originally Posted by gtr1000 View Post
    4) MAP sensor - not familiar with this so don't know what to expect
    Never heard of this one
    Perhaps you mean the MAF sensor
    Mass Air Flow sensor
    Used to ensure air is passing into the engine at the correct rate, the ECU adjusts the fuel flow to ensure combustion is at the correct rate

    Disconnect the MAF Sensor, the ECU then puts the engine into safe mode
    The ECU then assumes there is a constant rather than variable air flow, hence why the revs are lowered
    At high speed more air passes through the sensor but when it has failed (disconnected) the ECU does not monitor the sensor so has to reduce your vehicle speed so as not to damage the engine by the normal fuel to air ratio
    Last edited by m8internet; 21st November 2011 at 20:26.

  3. #3
    Regular Member marktaylor's Avatar
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    The scv's can block with a particle of dirt as small as 0.3mm I don't think they actually fail very often just block

    M8 internet , I beg to differ on your injector comment , I seen loads of instances of 1 injector failing and the other 5 being in perfect working order




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    I had a map sensor on my S4 but for the love of me I can't remember what it did

    Nick


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  5. #5
    Regular Member Celes's Avatar
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    Vehicle : Opel Signum

    Trim : Sport

    Engine : 3.0 CDTI

    Year : 12/03

    Default

    Quote Originally Posted by gtr1000 View Post
    1) SCVs - do they merely block up or fail/break? Why do they block up or why do they break?

    2) Injectors - do they gum up or fail/break? Same as above, either answer, why?

    3) EGR - does it block up or break? Same as above, either answer, why?

    4) MAP sensor - not familiar with this so don't know what to expect .

    Hopefully the answers from you gurus might help me and others.

    Oh, still haven't heard from admin about our sub forum.
    Here you have my point of view and my experience with these engine parts

    1. In my case, the SCVs (one or both) were sticking. The symptoms were rubbish start-ups (hot, and almost impossible to start cold) and random TOTAL loss of power coupled with trementous juddering from the engine - fuel starvation. I went to England with sticking SCV's and half of the way the engine was running superb, next morning in Germany I barely got the car going and I also had no power + judder. Then, as if it had a mind of its own, under full throttle in second and after 500miles of LIMPING through Belgium and Southern England, the car decided to reward me with all its power. The same story repeated itself the next day, with the exception that I had to use a start spray to get it going...

    2. Injectors usually gum up with soot and dirt particles that can't be filtered through the fuel filter. Usual symptoms are nailing (ticking noise under load from low revs) and MASSIVE grey smokescreen and usually rough engine. Here is the same car before an injector failed and after:
    Before - btw don't mind the smoke lol: [ame="http://www.youtube.com/watch?v=wGOKs7mf79A"]Defekter AGR-Ventil beim 3.0 V6 CDTi - YouTube[/ame]
    After: [ame="http://www.youtube.com/watch?v=NRvzAcaK6pA"]Signum 3.0CDTi with Injector problems - YouTube[/ame]

    3. The EGR valve on this engine is rather sturdy in my opinion. Just don't drive on low revs all the time. This particular engine, as any other would, likes a random italian tune up Stretch its legs every now and then...I drove my first 3.0 like a granny, but this resulted in cacked EGR and later blocked variable vanes in the turbo. If the EGR fails this engine will just go into limp mode (unlike the 1.9 which gets slower as the EGR gets dirtier), if the variable vanes in the turbo start sticking, the car will be rather unresponsive particularly under 2000rpm and over 3700rpm. This particular problem with the turbo can manifest itself as an underboosting (my case) or overboosting contition.

    4. MAP...maybe you meant MAF - mass air flow? Well, I had problems with this one too. The engine power/torque curve becomes all messed up. Mine felt like a bouncy castle. Low on power and in general I'd say the power band felt as if it was pulsating if you know what I mean. No fault codes produced.

    Rant over

    P.S. The vids are of my old 3.0CDTI
    Last edited by Celes; 21st November 2011 at 23:45.

  6. #6
    Regular Member m8internet's Avatar
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    Quote Originally Posted by marktaylor View Post
    M8 internet , I beg to differ on your injector comment , I seen loads of instances of 1 injector failing and the other 5 being in perfect working order
    Agreed, one injector can found to be the issue, usually due to a valve being at fault
    However, in the majority of cases it is simply wear and tear, the usual advice when one injector is found to be broken is to remove them all and inspect
    If the remainder are found to be in similar condition then remove them all, and many diesel specialists always advise to replace them all, even if two or more are found to be in good condition
    In a diesel engine they all need to be performing at or near full performance

  7. #7
    Regular Member m8internet's Avatar
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    Quote Originally Posted by gtr1000 View Post
    4) MAP sensor - not familiar with this so don't know what to expect
    I had to get on the phone to the mechanic I use
    This is the Manifold Absolute Pressure sensor, a new one on me
    This works alongside the MAF sensor to determine the density of the air passing into manifold
    This sensor is essential where the air pressure varies by altitude
    In turn this affects the EGR valve and whether the valve needs to be open or closed

    Now on the Y30DT this sensor should be sitting in the off position, until the EGR valve
    becomes active
    This should be easy to diagnose with fault code P0105 and part costs about £45
    Usual symptom is high revs followed by engine going straight into safe mode
    This might be what mine has been doing from time to time
    Last edited by m8internet; 22nd November 2011 at 00:01.

  8. #8
    Regular Member Celes's Avatar
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    Vehicle : Opel Signum

    Trim : Sport

    Engine : 3.0 CDTI

    Year : 12/03

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    Quote Originally Posted by m8internet View Post
    In turn this affects the EGR valve and whether the valve needs to be open or closed

    Now on the Y30DT this sensor should be sitting in the off position, until the EGR valve becomes active
    Hence why someone who blocked/blanked the EGR valve got the fault code for the MAP sensor.

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