My car is currently with the dealer (it's an 07 plate Octy vRS PD).

I have been having a problem where the car will suddenly and dramatically lose power whilst accelerating, particularly under load, and then suddenly the power will chime back in and all appears normal.

The problem seems to be worst when the motor is under load, eg in 4th/5th gear when accelerating up a hill like a motorway slip road. It feels almost like the turbo momentarily stops working, then smacks back in again, or like the passage of fuel/air is momentarily blocked off and then freed up again. As soon as the problem clears the car is fine once more. The problem doesn't appear to be made better/worse by atmospheric or weather changes.

So I booked the car in presuming that a quick check on the diagnostics would reveal the problem and allow the dealer to remedy it.

But no.

The machines say nothing is wrong. So the technician has taken it out to test and has experienced the fault for himself (not hard to do - drive everywhere in 4th and accelerate hard when the chance presents itself...). He has then spent the rest of the day trying to work out the fault, but finds nothing.

Can anybody more technically minded than me suggest anything that I ought to tell the tech to look for? It would have to be something that would not show up on VAGcom or any of the other diagnostic tools.

If it helps my car has about 27k on the clock, is used on the motorway daily (my commute is about 25 miles each way, 22 miles of which are m-way, so no DPF issues) and has never had any work done other than regular servicing and a fault on the air con fixed under warranty.

Yours head-scratchingly.

Soapy.

EGR valve?

Going into limp mode.

Phil

Technically that dont sound good. Wish i could offer some words of wisdom mate but im afraid it aint my forte. Still under warranty though....right???

Hope it gets sorted soon and you are back out on the road:thumbup:

Dan

Gadgetman - no, not going into limp mode, that's the strange thing - just happens then, er, un-happens and all seems well with the world. With careful driving it's possible to drive around the problem, but that's not really the point, is it?! Clarification on what 'EGR valve' is would be welcome too (sorry for idiocy...)

Dan - thankfully still under warranty mate, so I'm not too concerned about what they might find - just want them to find SOMETHING!

3pm on second day at dealers, and the phone is not a-ringing...

Intermittent faults are a nightmare. I've had a car that vibrates (like a slight misfire) when just on the throttle, and all told it's spent fifteen days being looked at and still no cure.

tis now 3.30pm on the second day at the dealer, and still the telephone do not ringeth...

tis now 3.30pm on the second day at the dealer, and still the telephone do not ringeth...

Grrrrrrrrrrrr hate waiting......let us know how you get on.

They lent you a car phil ?. pita without .

assuming its still under warranty , and bet that i didnt do it when the mechanic drove it.

its not sticky vanes is it? (or would that show up as a fault?)

Sounds very similar to the problems I have been having on my 1.9. Do you find if you accelerate in 4th from about 1000 / 1500 rpm that it sometimes stutters a bit, whereas other times it is as sweet as?

Skoda diagnosed either N75 valve or turbo.

Have changed N75 (£138 and about 10 mins to change) and no probs in about 350 miles. However, jury is still out!!

Good luck!!

its not sticky vanes is it? (or would that show up as a fault?)

Sticky vanes in the turbo usually causes an overboost error (which is recorded), then the engine goes into limp mode until the ignition is switched off and back on again.

It almost sounds like a fuel blockage to me, but I would have thought that would show an error code.

Maybe some data logs with VCDS might illuminate the mystery.

This is very interesting. I have a similar problem on my car (same engine, same mileage) but I put it down to the Custom Code map. Now you've got me wondering if it could be something else. It only happens when you plant your right foot hard after a siginficant period of gentle driving. A classic example of when it might happen is coming out of one of those REALLY long 50mph sections on the M1. Plant the throttle and you feel it just start to boost for a split second and then it totally loses boost.

Sometimes if you keep your foot planted it will stutter and power through it and be fine. Other times if you tried to keep the throttle in it would keep stuttering badly. If I feel it start to happen I quickly lift off and press the accelerator again and it's absolutely fine. So I've gotten used to driving around it. If you're driving enthusiastically, it never ever happens. Only ever after prolonged gentle driving.

I didn't have any faults come up in VCDS last time I checked.

Reckon it could be the same thing? When it happens on yours, can it happen at any time when you're accelerating hard or, like mine, only just after you floor it?

Edited 6 November, 200916 yr by wega3k

wega3k - sounds slightly different - mine is not restricted to hard acceleration after gentle cruising, it's whenever you strain the engine in a remotely enthusiastic way.

Anyway, update is that I have contaminated fuel! Garage rang this afternoon to say that one of the mechanics noticed it when the ethanol in the petrol started to wrinkle his barrier gloves. They asked if I have ever mis-fuelled the car (I haven't). It looks like I have bought diesel at a garage where they have contaminated tank and the engine is sensing it intermittently and cutting the fuel supply off as a failsafe.

The car is under warranty but, understandably, they aren't going to pay for that so I am going to have to set about pursuing the petrol company for the cost (£380).

Thinking about it, that makes sense. I always run the tank pretty dry then fill it up, so I am fuelling the car from dry about once every 10 days or so. The fault has only been happening since the last tank of fuel went in. There is no way it is a misfuel because if I had filled the tank with petrol then it would be PURE petrol and I would not have been going anywhere. Wife hasn't driven my car for months so she hasn't done it.

I feel some strongly worded missives on work letterhead coming up...

wega3k - sounds slightly different - mine is not restricted to hard acceleration after gentle cruising, it's whenever you strain the engine in a remotely enthusiastic way.

Anyway, update is that I have contaminated fuel! Garage rang this afternoon to say that one of the mechanics noticed it when the ethanol in the petrol started to wrinkle his barrier gloves. They asked if I have ever mis-fuelled the car (I haven't). It looks like I have bought diesel at a garage where they have contaminated tank and the engine is sensing it intermittently and cutting the fuel supply off as a failsafe.

The car is under warranty but, understandably, they aren't going to pay for that so I am going to have to set about pursuing the petrol company for the cost (£380).

Thinking about it, that makes sense. I always run the tank pretty dry then fill it up, so I am fuelling the car from dry about once every 10 days or so. The fault has only been happening since the last tank of fuel went in. There is no way it is a misfuel because if I had filled the tank with petrol then it would be PURE petrol and I would not have been going anywhere. Wife hasn't driven my car for months so she hasn't done it.

I feel some strongly worded missives on work letterhead coming up...

Do you have a good legal rep phil .... lol.

Gonna be fun when you tell what you do , can i come and listen

Think I might just go in, explain the problem, then when they try and fob me off I'll drop a business card on the counter...