Intermittent Loss of Power

sideways84

Hi guys,

I've just started a new job and have to drive through some pretty hilly areas. (Kallangur to Toowong for those in Qld) Occasionally when going around roundabouts or sharpish bends that arnt flat and that I'm accelerating out of, the power will drop off for a second or two and then come back on.

The car has 8000ks on it, does it no matter how much fuel is in it and has no engine mods. Has anyone had anything similar happen? Or any insight to why it may be happening?

Its booked into the dealer on the 3rd of May for a different issue, but I just cant make it there any earlier.

Cheers
Mark

Mikhailt

My guess would be traction control. Dropping your power down to prevent wheel spin.

Sambo

Mikhailt wrote: »

My guess would be traction control. Dropping your power down to prevent wheel spin.

X2


MY11 Candy White Highline. With lots of ARB goodies.

Sambo

@sideways84, can't remember your Rok, running standard with no additional weight from anything? I know that when I pick up a courtesy Rok from my dealer, it always seem so punchy after mine and I can make the traction control come on, where in mine it never would.


MY11 Candy White Highline. With lots of ARB goodies.

sideways84

The thing is it doesn't really matter how fast or slow I go into these corners the same thing happens, and I've never seen the light come on in above mentioned corners, maybe I'll try turning the traction off on a run to work and see if it makes any difference.

I do drive hard around other places and I've never had the traction interfere except hard on the power around a right hander taking off from a set of lights and this definitely feels different.

Oh and its unloaded on the way to work.

steveieh

hi sideways, the same thing happens to my rok, it is all ways in 3rd gear on a slight incline, i can do it all the time turning into the estate where i live, have put computer on vehicle and checked for codes but nothing, cant be arsed taking it to dealer to get the old no fault found BS, does yours do it on an incline?, is it in third gear?.

Steve.

sideways84

It does it on an incline and decline and now that I think about it I'd be in 3rd as well. Glad I'm not the only one cause it definitely doesn't feel like the traction control kicking in. How many ks has yours got on it Steve? And how long have you noticed it been happening for?

steveieh

mine has nearly 15k on it and is an my12, highline manual, been happening for a while now but as i said i have just been ignoring it, it is nothing to do with the traction control, it is more like something is going on with the gyroscope they have built in for the computer i think, due to the angle of the vehicle when it happens, one day i will get round to running it with a scan tool on to monitor the live data and see if i can find what is wrong!, have you mentioned it to VW yet?, how many km's has yours?.

Steve.

Calibrated

I used to drive that same route (and further, Kallangur to Darra every day), and never experienced what you're describing.


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Lynchie

Mine used to do it as well. Same thing, third gear going down incline after turning into our estate. Never noticed it happening anywhere else or on any other corner, just always that particular one. Thought I was imagining things!

sideways84

Yeah there's definitely something weird going on there, Steve mines a late my11 highline with 8000ks so id say our vehicles have the same mapping. I mentioned it to the service manager when booking it in for the other repairs and he just said that if it gets any worse they should have a look at it earlier. Its not life threatening, so it can wait, but ill be keen to see what they find when I give it to them on the 3rd.

Lynchie, is your remap an aftermarket one? Or did VW remap it due to another problem or upgrade?

And Ash, when you were doing you route from Kallangur to Darra, did you go through Bardon, near government house? There's a few corners through there where it is most frequent.

Lynchie

12345

TBRok

sideways84 wrote: »

And Ash, when you were doing you route from Kallangur to Darra, did you go through Bardon, near government house? There's a few corners through there where it is most frequent.

I used to get it a lot through Bardon. There a few drop offs where I'd have the accelerator down but no power. Such a weird feeling. But it's only a second and you're back on deck.



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Peter Jones

I have a descending right hand turn in my street that causes this every time. I think its the stability program being over zealous.
.
Prior to the Amarok I had a Bora and it did the same thing at that corner so its something to do with the way VW sets up the ESP and it's not just peculiar to the Amarok.

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flyingant

From all the descriptions I'd be willing to bet its the injectors being shut off completely. You may or may not be aware but when you're in gear but off the throttle, the injectors are not firing at all. This happens not just when you lift off the throttle completely but at any throttle position when the ECU decides that it can maintain speed without using fuel. VW seem to have gone a bit over the top with this as it comes on earlier than is ideal IMHO and until you realise what's going on certainly seems like a sudden loss of power.

It's all these little tricks however that all add up to one very frugal truck 👍


Cheers

Anthony

steveieh

flyingant wrote: »

From all the descriptions I'd be willing to bet its the injectors being shut off completely. You may or may not be aware but when you're in gear but off the throttle, the injectors are not firing at all. This happens not just when you lift off the throttle completely but at any throttle position when the ECU decides that it can maintain speed without using fuel. VW seem to have gone a bit over the top with this as it comes on earlier than is ideal IMHO and until you realise what's going on certainly seems like a sudden loss of power.

It's all these little tricks however that all add up to one very frugal truck ��


Cheers

Anthony

It is under accel Anthony not on decel, throttle pedal pressed down and no response, feels like you haven't pressed accel pedal.

flyingant

I'm hearing you but are you increasing the throttle at the moment it happens or holding the same position?


Cheers

Anthony

beng5328

What happens if you slip the triptronic into another gear at that moment?

forrestmount

My rok does the same thing, won't do it everywhere but going over successive hills a few weeks back the throttle seemed to have no effect towards the bottom. I was trying to accelerate near the bottom but the rok wasn't keen. The car lost revs but maintained speed. It was very predictable so thought it was a safety system

steveieh

Holding throttle, but when no response increasing.

steveieh

beng5328 wrote: »

What happens if you slip the triptronic into another gear at that moment?

Mine is always in tiptronic........it is a manual.

flyingant

Maybe it's a combination of the injector shut off and the TCS. For example; you've sensed the power loss from the shut off and respond too much/quickly which brings in the TCS to keep a lid on things.

I don't know, I'm just throwing ideas around. I don't have the problems you guys describe, or at least to the same magnitude.


Cheers

Anthony

Steevo

I think I experienced the same thing you folks are talking about when rounding a tight-ish right hand hairpin bend.

The road was wet but it wasn't raining, I was rounding a downhill right hander, I had just gotten on the gas after apexing the corner, I didn't sense any understeer or tyre scrub at any point before the apex, it was almost like I had a flat spot on a vehicle with a carbie and no traction control light that I noticed, it all happened pretty quick.

I thought WTF just happened then this thread came to mind. ;-)

STV_87

flyingant wrote: »

From all the descriptions I'd be willing to bet its the injectors being shut off completely. You may or may not be aware but when you're in gear but off the throttle, the injectors are not firing at all. This happens not just when you lift off the throttle completely but at any throttle position when the ECU decides that it can maintain speed without using fuel. VW seem to have gone a bit over the top with this as it comes on earlier than is ideal IMHO and until you realise what's going on certainly seems like a sudden loss of power.

It's all these little tricks however that all add up to one very frugal truck 👍


Cheers

Anthony

I'd have to agree with Flyingant.
I have noticed when I come up over a crest then down a significant decline, i notice that when I go to accelerate hard down the hill (like anyone would ) there's a delay of maybe 2-2.5 seconds as a guess.

And yes the injectors would shut off completely when off the juice, the trip computer tells us this when it reads 0.0L/100km

steveieh

STV_87 wrote: »

I'd have to agree with Flyingant.
I have noticed when I come up over a crest then down a significant decline, i notice that when I go to accelerate hard down the hill (like anyone would ) there's a delay of maybe 2-2.5 seconds as a guess.

And yes the injectors would shut off completely when off the juice, the trip computer tells us this when it reads 0.0L/100km

Mate the injectors are piezo electronic it is a less than millisecond between when they shut off and fire again, any normal person would never notice this!, if it was a case of injector shut off the same delay/loss of power would occur when coming to a junction, it never does, it is always on. Slight incline decline and always in 3rd gear, I have tried to simulate it at slow speeds in the same spot it always does it in second gear and can never get it to do it.

Steve.

flyingant

Steve, they fire in synchronicity with the pistons. When you lift off the throttle while in gear they are off for however long that continues. If you are coasting down a mountain without touching the throttle for 10mins then they are off for 10mins.

There is no direct link between throttle and engine anymore. You use the throttle to tell the ECU what you want the engine to do then it decides how to get it done. Sometimes what you want and what the ECU want is different. Cresting a rise then going to boot it down the other side is a good example. You say 'accelerate' but because gravity is accelerating you already the ECU says 'nup, not using any fuel for what I can do for free'.


Cheers

Anthony

steveieh

flyingant wrote: »

Steve, they fire in synchronicity with the pistons. When you lift off the throttle while in gear they are off for however long that continues. If you are coasting down a mountain without touching the throttle for 10mins then they are off for 10mins.

There is no direct link between throttle and engine anymore. You use the throttle to tell the ECU what you want the engine to do then it decides how to get it done. Sometimes what you want and what the ECU want is different. Cresting a rise then going to boot it down the other side is a good example. You say 'accelerate' but because gravity is accelerating you already the ECU says 'nup, not using any fuel for what I can do for free'.


Cheers

Anthony

Thanks for that Anthony, being a mechanic that specialises in European vehicles BMW,VW,Benz etc for the last twenty years I know exactly how they work.
What I am trying to say is that unless you have felt it your self it is hard to define, but one thing is for sure it is nothing to do with the vehicle deciding it needs no injection as it is going down hill, as you press the throttle going down or up hill the vehicle should respond, in this case it doesn't.
I believe if you look back some people have had it happen going up hill where there is nothing pushing the vehicle along.
As I said I am going to put My scan tool on mine and simulate it whilst monitoring live data to see if I can find what is going on.

Steve.

beng5328

Thanks for the technical discussions guys. I'm just watching and learning - keep it up as I'm interested to know more....

flyingant

steveieh wrote: »

Thanks for that Anthony

No problem.




Cheers

Anthony

STV_87

steveieh wrote: »

Mate the injectors are piezo electronic it is a less than millisecond between when they shut off and fire again, any normal person would never notice this!, if it was a case of injector shut off the same delay/loss of power would occur when coming to a junction, it never does, it is always on. Slight incline decline and always in 3rd gear, I have tried to simulate it at slow speeds in the same spot it always does it in second gear and can never get it to do it.

Steve.

Yes I understand how piezoelectric injectors work and yes they are capable of opening 10 times per 5 milliseconds. By varying the voltage and current sent to the piezoelectric crystals, via the injector driver transistor, the injector opening time and injector opening bandwidth can be controlled thus extremely accurately controlling the amount of fuel that is sent for burn. State of the art shit!

I think your missing the association we are trying to colligate though.
What I was trying to point out (and i think flyingant was also trying to point out) is that when traveling downhill, the ECM doesn't send a signal to the injector driver transistor. We are simply pointing out the correlation of the injectors not operating when traveling downhill and the delayed "pick-up" if you will, when attempting to accelerate further down the hill. Perhaps the computer has trouble recognizing when to allow diesel to be injected due to this and perhaps this error only occurs when in 3rd gear. After all, the computer knows everything the car is doing. Being a mechanical engineer, I would be inclined to stand up and blame the computer systems and or electrical engineers for dodgy programing

Are you sure the delay your describing when driving uphill isn't a result of turbo(s) lag? After all, the engine is only a 2L and the turbos are trying to develop 22 odd pound of boost whilst propelling a 2 tonne truck up hill. I have made this observation when in 3rd gear with insufficient revs.
I also drive a new BT50 (5 cyl, 3.2L) for work and when traveling up the same hill in 3rd gear, there is an atrocious amount of turbo lag followed by a massive kick in the ass when the turbo finally comes out to play.

Regards

Mikhailt

STV_87 wrote: »

Being a mechanical engineer, I would be inclined to stand up and blame the computer systems and or electrical engineers for dodgy programing

I hear you, mate!:D