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Occasional "Panting" Noise – Mechanic Says Misfire?

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10:28
January 20, 2011


hu88ertvelsat

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Post edited 10:30 – January 20, 2011 by hu88ertvelsat


Hi,

For a little while now, my Vel Satis has made a strange noise accompanies by a weird feeling, only occasionally, and it doesn't seem to affect things.

What happens is, you can be driving along steadily at any speed and sometimes the engine "feel"/sound starts to become slightly muffled almost as if someone has put their hands over your ears – and then it's quickly followed by a very slight rocking and more notably, a cyclical noise almost like a large dog panting with its tongue out (and sounds/feels slightly like the rear wheels aren't getting traction). To get rid of the panting noise and slightly odd feel to the engine/drive train, all I need to do is very gently either slow down and gently accelerate again, or gently accelerate. The panting noise and odd engine feel both immediately go away, and things seem fine. The noise/sensation does appear to be coming from the middle or rear of the car, not the front, I don't think (though could be wrong). It kind of feels like the car is struggling slightly because it's in the wrong gear, so perhaps gently (not kick-down!) pressing or easing off the accelerator pedal makes it change gear (not that I notice it changing up or down, so maybe I'm wrong!).

No stop or warning lights have ever come on when this panting noise happens and performance seems normal, with the same MPG as usual, etc, etc.

A mechanic I took for a spin one day (about something else) said it's engine misfire and maybe one of the cylinders/injectors is blocked, so he suggested trying injector cleaner. I did do, for the last 6-8 months, but no difference – getting slightly worse, in fact.

Any ideas chaps?

PS – Notes: (been researching, just to show I'm proactive as usual!)

  • Problems with DPF (Diesel Particulate Filter)
  • EGR Valve
  • Blocked Injector/Cylinder
  • Broken Motor Mount

My engine has felt and sounded rougher lately and I also get an occasional rubbing sound from the OSF wheel area, so perhaps the odd "dog panting" sympton when driving is also the same thing i.e. a broken/loose motor mount or some other mount?

Anyway, will wait for your thoughts. Don't want to pay dealers' rates straight away without researching and posting on forums.

00:59
January 24, 2011


Rosic

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Post edited 01:01 – January 24, 2011 by Rosic


Hi!

I'm not really sure, how to interpret the panting noise.
Anyway what engine You have in your car?

Did You try to put into manual gear change and lower the gear when it starts to happened? Maybe there is some fault on gearbox and it didn't change gear properly.

As far as I know Vels don't have a DPF/FAP filers, they are too old for that :P
EGR – might be, but you should notice a lot of black smoke behind You.
Blocked injector – i never heard about any problems with blocked injectors in this car. more often there are likely to overflow fuel, causing damage to engine by burning the pistons.
If there will be problem with an engine mount you will feel it especially when You rough accelerate or kick down. it will be more like a single kick noise.

I will suggest to go somewhere to connect you car to clip and see errors. It may say something even if it's not displayed on dashboard.
Then clean the EGR valve.
As far as I know it may be a fault of the 'stop' sensor under your break pedal, or throttle sensor under your gas pedal.

I hope I help at least a little.

and btw. don't listen to random mechanics! When they see Vel Satis, they believe that it is a spaceship! :P

08:50
January 24, 2011


hu88ertvelsat

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Helllo Rosic,

Thank you for your reply to my problem! My car is a 3.0 DV6 automatic.

Actually, I did think about using the car in "manual" mode, which I never use..but I have not tried it yet.

When my wife drives her VW (manual) I listen to the sound of her engine and everything, and I try to compare it to mine, and I think it must be something to do with my gearbox, as my car never makes the "panting" noise or feeling, if I drive it with enthusiasm, a little harder than normal. The panting noise only happened when I'm driving it gently, perhaps too slowly, or slow enough for the car to be in a too-high gear at the speed I am doing. As soon as I accelerate, or slow down a bit, the panting noise and slight rocking sensation disappear.

There is never any black smoke behind me. Only sometimes a small amount of light grey smoke when I kick-down, after I have not used my car for a while. But this is just the car clearing any normal diesel build-up, I think.

Thanks! And welcome to the forum by the way!

22:36
January 26, 2011


Rosic

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Hi!

Did You try the manual gear switching?
I truly hope that is not a gearbox issue, because sorting that out will cost a fortune.
Much better if it will be EGR or one of the sensors under Your pedals.

When accelerating diesel there is always some grey/black smoke behind. There is no way to avoid that, so not to worry about that.
It is not a self cleaning issue. The self cleaning have place only when you have FAP (DPF). Vels don't have it. Anyway, black/grey smoke when accelerating is just not properly burned fuel – a normal thing. All diesel engines when accelerating hard are a little overflowed by fuel that is why we have a smoke. When one of your injection will break down you will have similar smoke, but much more and always. EGR fault is producing rather very black smoke, because of wrong exhaust gas circulation.
Anyway it still may be EGR.

11:19
February 2, 2011


hu88ertvelsat

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I have been researching this "panting" noise some more on the Internet and it may be something to do with the fuel pump, what do you think?

Also, I found some info saying that using diesel additive (injector cleaner) can damage the pump, and even that using high quality diesel like Shell Diesel V-Power, can also damage the fuel pump, which may result in this "panting".

Oh dear, the mechanic who drove my car several times, said he was quite sure the "panting" was an engine cylinder misfire and he told me to put some diesel additive injector cleaner in the tank, even in high concentration, as this may unblock the dirty injector/cylinder.

But my "panting" has got worse over the last 6 months, especially when I am driving gently 1) in cold weather 2) up an slight or a steep incline and 3) driving quite slowly, so maybe the car is in too-high a gear.

Maybe I should stop putting Millers in the tank regularly after filling up, and see if the "panting" gets a bit better?

The strange thing is, the car feels and performs fine, no drop in MPG, no warning or stop signs, nothing. Just this "panting" sound and a slight rocking, when going up an incline quite slowly. A tiny blip of the throttle gets rid of the "panting" straight away. Weird!


 

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