Had the car for a few years only done 40k millage just had cambelt and full service and the day i picked it up i drove home normally not thrashing it or anything was doing 70mph down my local bypass when i got a jolt forward as if someone had just tapped the brake momentarily . At the time i wasn't excallerating or decalerating just maintaining the same speed. as you can imagine this scared the hell out of me so i backed off and drove home very cautiously the next few days i forgot about the problem. However on the same stretch of road its done it again another three times. I took the car back to the same garage who happen to be indipendent but approaved VW specialists. They showed me the diagnostics on the touch screen pad thing and everything had green ticks against it with no registered faults. The guy said it could be overboost pressure but im nots sure any one have any ideas? because it scares the crap out of you when it just momentarily lunges as if someone has tapped the brake pedal. The lights dont dip or anything so seams more mechanical than electrical. Help someone please!

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Skoda Octavia VRS 20v 2.0FSI Turbo + Audi A4 (B5) 1.8SE

Did you notice anything like huge powerlines or military radar nearby when it happened? Only reason I ask is that it was the same stretch of road every time but perhaps thats the only place you have done the same speed recently. Bit of a puzzler.

Did you notice anything like huge powerlines or military radar nearby when it happened? Only reason I ask is that it was the same stretch of road every time but perhaps thats the only place you have done the same speed recently. Bit of a puzzler.

There are power lines and a mobile phone mast infact its right next to a huge hill with a transmitter on it but can't see any of this being of the same frequency to cause any electrical interference. Plus i have used this road right next to my house for over a year with this particular car and no problems. It seams to be the cam belt change or full service that has triggered something. Took it back to the garage but because its intermitant and difficult to replicate for them its hard to trouble shoot. When they changed the cambelt kit they used genuine VAG parts and they changed the waterpump as a precaution. But other than reseting the service light on the dash i don't think they have touched anything electrical. I thought maybe it could be some crap in the fuel tank? or a ridge in the disk/loose pad that suddenly vibrates and sticks momentarilty but i really am clutching ats straws. I was hoping that someone would read this and have experienced a similar problem or have an idea what it could be. The best way i can describe the fault is that its like someone leaning over and pressing your brake pedal and releasing it very quickly. only lasts a fraction of a second but its enough to give you a quick jolt. I have checked the last couple of times that my right foot hasn't caught the brake by accident but my foots allways been miles away from the pedal.

sounds daft but when you go over the same bit off road are you going over a bump or anything in the road which will cause the car to move?

reason im asking is i had the same problem with a focus i had and it ended up a earth strap wasnt tightened

full service

Could it be anything to do with the fuel supply? Dodgy fuel filter fitted at service time?

Crankshaft sensor been disturbed during the service / belt change, maybe isn't 100% secure or terminals aren't clean?

Dodgy or disturbed sensor / gyro causing the ESP to kick in as you go over a bump and apply a brake(s)?

How repeatable is the problem? Everytime you pass that spot? Or just sometimes?

Could it be anything to do with the fuel supply? Dodgy fuel filter fitted at service time?

Crankshaft sensor been disturbed during the service / belt change, maybe isn't 100% secure or terminals aren't clean?

Dodgy or disturbed sensor / gyro causing the ESP to kick in as you go over a bump and apply a brake(s)?

How repeatable is the problem? Everytime you pass that spot? Or just sometimes?

Not repeatable just occasional don't think its a bump in the road its new tarmac on a recently built dual carriageway.

wil keep you posted on any updates that might help diagnose problem.

I have a mk1 Octavia 1.8T and had what sounds like a similar problem a while back. It was very occasional at first, but gradually got more frequent to the point where the car was just undrivable. It turned out to be a faulty mass airflow sensor/meter thingy. Apologies, I'm not very technical.

It could be wheel spin, if that strech of road is slippery. Is that road a bit uphill and was the revs around 2000rpm, in that case, it might be misfire.

It could be wheel spin, if that strech of road is slippery. Is that road a bit uphill and was the revs around 2000rpm, in that case, it might be misfire.

IT does feel like wheel spin , however how do you get wheel spin @70-80mph @ 3k revs and have been doing this constantly for 5 minutes i did think

id hit a patch of oil or something first few times but it happens on both sides of the carriageway at different times. the roads pretty flat but off camber

and long sweeping bend. I defo think its mechanical, brake related or engine / fuel related. i think the stretch of road is coincidental just that thats

the only road i use everyday where its 70 mph+

Thanks to everyone for reply's so far its all food for thought!

It could be wheel spin, if that strech of road is slippery. Is that road a bit uphill and was the revs around 2000rpm, in that case, it might be misfire.

IT does feel like wheel spin , however how do you get wheel spin @70-80mph @ 3k revs and have been doing this constantly for 5 minutes i did think

id hit a patch of oil or something first few times but it happens on both sides of the carriageway at different times. the roads pretty flat but off camber

and long sweeping bend. I defo think its mechanical, brake related or engine / fuel related. i think the stretch of road is coincidental just that thats

the only road i use everyday where its 70 mph+

Thanks to everyone for reply's so far its all food for thought!

try driving on another road at 70 -80 mph maybe a bit more , it might only happen at a certain speed that sometimes you hit and sometimes you dont!!