 | Home > Puma (Tdci) > Eratic Idle especially when cold |
 
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17382   
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Have you checked for logged DTCs (fault codees)? It sounds like a classic symptoms of Volume Control Valve failure, as currently under discussion elsewhere on this forum. If it is there VCV there may well be no fault codes logged.
The part is fairly cheap (Ł130) and easy to fit, but you will need to carry out a fuel pump recalibration cycle afterwards. It is possible that simple carrying out the recalibration with the current valve may sort the problem, depending on whether the valve is faulty or simply that its characteristics have changed with time. It is worth changing the fuel filter too, and check for water and/or the dreaded black slime at the same time. The VCV is very susceptilble to damage if there is water or slime in the fuel. The EGR valve could also be causing these symptoms, but if so it is likely that there will be DTCs pointing towards it. |
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15th Jul 2014 11:39am |
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| OleDave Member Since: 19 Oct 2013 Location: CARDIFF Posts: 175 
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Hi Blackwolf and thanks for the reply, no I have not had it checked for ECU faults as no engine management light have come on, I suppose it is possible that the ECU might not record some problems so will have it plugged in soon to see.
I am not sure what you mean about recalibration of the fuel pump? do you mean similar to a remap? Can you advise where the volume control valve is situated? Will change the filter and see what happens. Many Thanks for your help Blackwolf Regards Ole Dave |
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15th Jul 2014 12:52pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17382
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On a 2.4 Puma the VCV is located on the combined LP/HP fuel pump in the engine bay, as shown in the photo below (which I have pinched from a post Pete Bell made recently in another thread.
The purpose of the VCV is to regulate under control of the ECU the volume of fuel being supplied from the LP stage of the pump to the HP stage, and hence the rate at which fuel is delivered to the high pressure common rail. The Fuel Pump Recalibration process (often referred to as a "pump relearn" or similar) is a process initiatied from a diagnostic tool such as Faultmate which causes the ECU to calibrate a particular VCV (since they all perfomr slightly differently) by modulating the VCV to learn the flow rates for different settings. The calibration data is then written into the ECU memory so that the ECU can acrruately regulate the VCV according to its own particular characteristics. If the calibration process has not been carried out, or if the VCV has been changed and not recalibrated, or if the VCV is not working properly, or if, as seems to happen occasionally on my Puma, the ECU seems to lose the calibration data, the effect is that the flow rate from the LP to the HP stages of the pump is not correctly matched to the demands of the engine. This can cause fluctuations in common rail pressure which may not be sufficient to cause DTCs to be logged, but can affect the smooth running of the engine. When my original VCV packed up the vehicle fdeveloped a massive "flat spot" and simply wouldn't accelerate. As it got worse, it would stall at idle. However no DTCs were logged at all. Generally speaking, if a TDCi is running badly look first for DTCs, whcih may well point to the probelm, however if there are no DTCs logged then suspect the VCV. |
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15th Jul 2014 1:56pm |
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| OleDave Member Since: 19 Oct 2013 Location: CARDIFF Posts: 175
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Well Blackwolf wonderful, that was more than I expected and described it in detail, I initially thought you might be referring to the mass air flow meter but now I see what your saying about the fuel regulation and the valve which controls it, I will have the beast plugged in possibly tomorrow or Thursday as I am due to visit the garage as they are mates of mine. Will let you know the outcome if anything found.
Many many thanks Regards Ole Dave Just another quickie Blackwolf, the drawing shows two items, could you identify items 1 and 2 as I think item 2 is a fuel pressure regulator sensor? Regards Ole Dave |
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15th Jul 2014 2:06pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17382
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Yes, sorry, I should have identified it!
The VCV is item 1 (at the top of the pump), item 2 is the fuel temperature sensor. |
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15th Jul 2014 4:31pm |
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| Cheshire110 Member Since: 26 Jul 2013 Location: Cheshire/London Posts: 2755
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also can be worth cleaning the MAF sensor, a couple minute job which costs nothing but a can of MAF sensor cleaner which is widely available. Failing that just take it out and inspect/blow it clean. (don't touch it or be too harsh on it)
searcg 'cleaning MAF sensor' on youtube there are many videos. worth ruling out first. Cheers, David Land Rovers of all shapes S3 onwards… Daily is a 110 V8. |
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15th Jul 2014 4:41pm |
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| OleDave Member Since: 19 Oct 2013 Location: CARDIFF Posts: 175
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Thanks guys, I had thought of cleaning the MAF sensor David as in the past I have found that that can have an effect on the engine idle when it sends the wrong signals to the ECU. its strange as its most noticable when cold, when hot it goes?
Regards to all Ole Dave |
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15th Jul 2014 5:02pm |
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| Cheshire110 Member Since: 26 Jul 2013 Location: Cheshire/London Posts: 2755
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Yeah, I guess if the computer's making changes to fuel/air based on not correct data the result will be poor running. But that's just a guess
Would be helpful if you can get a code reader. Even a cheap ebay Bluetooth obd reader and a cheap smartphone app would be enough to give simple codes, then just search up the meaning online Cheers, David Land Rovers of all shapes S3 onwards… Daily is a 110 V8. |
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15th Jul 2014 5:13pm |
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| OleDave Member Since: 19 Oct 2013 Location: CARDIFF Posts: 175
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Hi David, well I am a little bit lucky in one respect as being a retired auto technician I have access to the garage I worked for before I retired, they have a Bosch code reader and a few other expensive pieces of equipment which I could never ever afford to look at codes, hopefully they will have a defender puma pod and somat will show up?
You have all been very helpfull again, this is a fab forum with so many helpful people Many Thanks Regards Ole Dave |
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15th Jul 2014 7:40pm |
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| bell-auto-services Member Since: 08 Jul 2007 Location: North Yorkshire Posts: 2232 
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Water in fuel from a split fuel tank breather generally can sometimes cause iratic idle without a MIL showing. But as said its very very common for the VCV to fail and do the very same.
Regards Pete |
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15th Jul 2014 8:53pm |
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| OleDave Member Since: 19 Oct 2013 Location: CARDIFF Posts: 175
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Hi Pete, thank you for your info as all the others, as mentioned I am going to change the filter first and have a look for the dreaded black slime or water! I somewhat doubt there is any as my gut feelings now are that the volume control valve is faulty, I have since receiving all the replies on the problem considered removing the valve at some point and giving it a good wash, I have done this with some some EGR valves with great success but not sure if the vcv would appreciate a good scrub!! or even if it would cure it?
Maybe you could comment on the above Pete? Regards Ole Dave |
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16th Jul 2014 8:34am |
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| bell-auto-services Member Since: 08 Jul 2007 Location: North Yorkshire Posts: 2232
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From experience I have found when the old VCV is removed their is nothing to see in most cases, infact it looks like new with no marks or scuffs etc etc and if you didnt know by looking at it it would look new and normal.
I can only arruse the internals that cant be seen are the failing part. pete |
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16th Jul 2014 8:47am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17382
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I'd second what Pete says - there's really no point trying to clean a VCV. It is very unlikely to make a difference and if you clean it and put it back and the fault is still present you'll be tempted to look eslewhere.
Advice I received from an excellent and honest main dealer who's changed many VCVs is that it simply isn't worth doing anything other than replacing it. If you replace it and find it makes no difference then you know you have a working spare fir when it does eventually fail (note "when" not "if" since it will fail one day)! When you take the old one off it will look perfect even if faulty. It is worth bearing in mind that it is a very precision-made part with very small metering openings, and an imperceptible amount of wear or damage which you cannot possibly see will render it useless. The only saving grace is that it is reasonably accessibly and you don't have to be a mutant child to reach it! Takes about 10 minutes to change the part. Add in warming the engine and doing to pump relearn and the whole job is 1/2 to 1 hour. |
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16th Jul 2014 9:02am |
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| OleDave Member Since: 19 Oct 2013 Location: CARDIFF Posts: 175
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Hi guys and thanks again, that tickle me Blackwolf where you said even a mutant child could change it! however when working on my own vehicles nothing ever seems to be straight forward!!
Is the vcv only obtainable through a dealer or can it be bought elsewhere? Regards Ole Dave |
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16th Jul 2014 9:42am |
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