bk1

Hi, I know this has been mentioned in older threads, but my 1.8T 2004 MkI Elegance (14k miles) drives really jerkily for the first minute or two after a cold start, then seems to behave itself.

It never used to do this - it started a month or so ago.
It starts fine, with the usual vibration/rattly noise that last a few seconds, then that calms down a bit, and the revs sit at about 1200, with a fair bit of general buzziness still being heard.

This morning, I sat and waited instead of driving off straight away as I normally do, and after maybe a minute, the revs dropped from 1200 to 1000 (normal idle speed for my car) and the buzzy sound disappeared, leaving a smoother engine note.

As I drove off, there was no sign of the jerkiness that I have been getting lately.

My question is: what is the engine doing that makes it sit at higher revs? Is it trying to get to a warmer temperature before it cuts fuel a bit and is happy to idle at lower revs?
Why would this cause jerkiness as I drive, if the engine is being fed more fuel to try and deal with warming up, etc?

I'm curious as to why I'm seeing this behaviour now (especially in summer - I'd expect jerky warmups more in winter). I am probably due a service soon - perhaps that will help smooth things out a bit.

Many thanks for any thoughts people might have,
Ben

SkodiRS

This is normal...for the first minute the ECU is true to throw loads of fuel in to get the CAT up to to temperature for emissions.

I always wait for a couple of minutes or at least until the revs drop back to normal idle before driving off....otherwise as you have experienced it wil be a bit jerky.

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Adrian.

bk1

But why has it only recently started doing it?

cheezemonkhai

Get a VAG com on it and see what the engine says?

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DGW

Can you hear any noise from the secondary air pump immediately after startup, ie is the pump working?

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Denis

2002 Octavia 1.8T 4X4 turbo Estate - rebreathed on by Jabba ... 31.93mpg
2007 Fabia vRS - CC, ESP and full leather trim by Seat Surgeons ...48.57 mpg...

bk1

No idea - what does it sound like, and where is it located?
I think I'd have trouble picking things out to listen to, as the engine is pretty noisy until it calms down.

orinj

That answers a potential query I had on my Octavia vRS. When I start the engine from cold the biting point on the clutch is much more sensitive and the car tends to shoot forward much quicker than normal if I'm not careful.

Normally I can get the car moving from a standstill using only the clutch (if I want to) but when the engine is cold I must use the throttle to prevent it from stalling. I guess this is normal.

bk1

So where is this secondary air pump and what should I listen for?
My revs sit at 1200 for about a minute, then drop to 1000. Engine note quietens a LOT, but note is still not a nice purr - revs still wander around a bit.
After fully warming up, revs sit at around 800.

I'm thinking that this could be o2 sensors, as that would make sense - engine might not be getting fuel amount right and that would explain jerkiness.

Thanks,
Ben

jos

I had a very similar problem on mine. I hooked it up to VAG COM and got error code 17978 which I didnt think was anything to worry about. I got fed up with the jerking so booked it it and the error code was rectified by the mechanic wiggling some wires. Not the best of resoloutions but its sorted it any way.

Try to get it onto VAG COM and see whether any errors are present.

bk1

I'm still getting this. I had 1st variable service a week ago and guy said to book it in and leave it overnight so they can have a listen in the morning. I think I'll do that, as the car didn't used to do this, and it's quite annoying to have to sit and wait for the revs to calm down. It takes just over a minute and I'm normally a couple of corners from home by then - if I drive off without waiting then car can jerk quite strongly.

Seems to me that the secondary airpump is doing too much, and making the wrong air:fuel ratio, hence the jerkiness. I assume it's too much air, as I think the pump works by pumping more air in to help warm up the cat, etc?
Does the secondary airpump always work in harmony with the fuel delivery, or can the airpump go AWOL and mess up the mix?

jas328sport

my vrs is exactly the same as this,if you wait for the secondary pump to stop,approx 1 minute then it will drive perfectly.if you try and drive off straight away then it is also jerky for a while.mine didnt do it when i got it and has so far had a new dv and maf which havent cured the problem so i have just learned to live with it now.
are everybodys cars like this or is something not right because bk1's car and mine have exactly the same symptoms and can be a bit embarassing sometimes especially when leaving work as i get enough stick for driving a skoda as it is without giving them more ammunition to take the wee

bk1

I was just reading this: http://www.12v.org/engine/index.php?section=hw&sm=2nd
Which kind of confirms what I understood about the 2ndary airpump and the way it works.
It also makes me wonder if a dodgy o2 sensor could be causing the airpump to remain active, because if the o2 sensor isn't reading correctly then the airpump would be told to keep going...
Anyway, I have just booked mine in to be looked at on the 5th Sep. I'll post here about what (if anything) is found.

ag.morley

Jerky when cold, then warms up


Sounds like the wife...........................

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bk1

Update: I dropped the car at the dealer last night so they could start it cold this morning, and they just called to say that they found 2 things: the air pump and throttle body were "bunged up".
They even want to keep the car overnight again so they can make sure it's ok tomorrow morning. Sounds like very good service to me.

It does mean I get another night in the 1.2l Fabia HTP tub, but I don't mind - it's fun to drive.

MC Bodge

where is the 'air pump'?

There seem to be a huge number of causes for these jerking and hesitation issues....

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Mk1 Octavia vRS. The thinking man's Hot Hatch.
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TKW

Yes, I wouldn't mind having a go at "unbunging" these on mine too

I seem to remember there was a guide to cleaning the throttle body somewhere. Anyone got a better memory than me?

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Octavia 4x4

bk1

Note that this jerkiness is an issue only from cold start, and only for a short amount of time, and it is definitely related to the 2ndary air pump - see my comments earlier in this thread about what this pump does.

If you have jerkiness when sitting at traffic lights, or when accelerating hard, then you're talking about a different problem.
I say that, although some people have found that getting the throttle body cleaned will reduce the jerkiness you get when the engine is idling.

Other people have problems with a hesitation when accelerating hard, almost as though the turbo pauses and then goes again. From what I have read, that problem can be a real pig to diagnose.

I'll see if I can ask them exactly what had "bunged it up" so I can avoid it in future, etc. Chances are that I won't get to talk to the technician, but I'll see what I can find out.

Chris Miles

From my experience they all do it, this goes for mine and my friends Vrs. Interestingly they don't seem to do it from new but deteriorate over time, so what changes that is common to all models with the 1.8T?

888

This is exactly what mine does (VRS) from cold you notice the revs are about 1,200rpm at tickover, and if you drive off whilst they are still high, its so jerky over about 1,800rpm. But if you wait a min, the revs drop back down to 800rpm and the car is normal. The local Skoda dealer put it on VAG-COM and i have 17705 error code!! there are so many threads about this bloody code!! i wouldnt know what to start replacing to fix it (do a search and see what i mean), but as its only for the first min of any drive, im not fussed. I would normally let the car warm up anyway, so not fussed. But VAG-COM is best bet.