Sounds like a tractor on start up?

[Gmlyall]

My Scirocco sounds really rough on start up from cold intermittently-55000 miles on clock. Is it the timing chain???

[balli931]

Could be bud. Does it rattle for a few seconds then stop ?

[Gmlyall]

Yeah quite an alarming rattle then nothing. And sometimes it doesn't do it!

[froudeg]

There are numerous issues with this engine which occur during a cold start:

A very loud rattle / grinding noise coming from front right of the engine

This is caused by the camshaft adjuster sticking during startup. Early revision (pre 2011) camshaft adjusters intermittently stick for a few seconds during startup.
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A less loud chain rattle, lasting either a few seconds or minutes, again from the front right of the engine

Caused by a faulty / sticking timing chain tensioner. The chain tensioner can fail or stick during cold starts, meaning there is little tension on the chain - a dangerous situation where the chain can slip a tooth or two and end up ruining the engine. Other than changing the tensioner (and chain as a precaution), there is no other solution. Proper oil changes as per service (or more frequent if doing mainly short runs) can help prevent chain tensioner sticking.

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Cold start poor running for 30 seconds or so, making a burbling/popping noise from the exhaust and somewhat rough running (can feel shimmers in the cabin)

Caused by ECU software glitch during pre-cat heating on a cold start. This rough running only occurs on a cold start where the coolant temperature is approximately between 19c and 32c...your dash air temp will closely follow this on a full cold start so can be used as a rough guide of when it will happen. The engine will misfire for 30 seconds during startup under these conditions, making the exhaust pop, burble and rattle with the engine sound rough. It can also occur if you have done a run and let the engine cool down to the point its again in this temperature range and then you restart. There is no solution to this at present as its a fueling issue cause by the ECU, and latest ECU firmware doesn't fix it...as a temp fix if you hear it running rough like this, stop engine and restart - it won't do it again as it won't do the precat heating if the engine has very recently been started.

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Finally all these engines will make a bit of a diesely like sound on a cold start for 10 seconds or so, and run with high rpm.
This is normal as the engine will overlap exhaust and intake valve timing as part of the process to more rapidly heat the engine up - during this phase it will run at high rpm of approx 1100 and settle down to 700ish after 30 seconds.

Normal startup noise
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and

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[Gmlyall]

I think it sounds very like the first one! Is that a costly repair? Thanks for your help!

[froudeg]

A sound like the first one is one not to worry about as it doesn't do any harm (other than making the horrible noise).
If it is the first one you will find it happens more frequently in the winter (colder weather). It will also happen more as you get closer to your annual oil change.

The fix is expensive - the newer design camshaft adjuster from VW costs £400, although the same genuine part can be picked up elsewhere for £200.
The problem is the labour - to change the camshaft adjuster is the same work to get to the timing chain / tensioner as if you were changing those - which is a LOT of work, I would expect a repair bill from VW for just labour to be in the order of £700- doing it elsewhere would probably be half that for the labour.

My car has the exact same problem, but it only sticks rarely on startup (say a few times a year) - reason being is I do oil changes every 5000 miles and every 20,000 miles I do an oil flush. Just preventative maintenance that stops this camshaft adjuster sticking. Really I should get it changed, but I don't fancy doing the work myself atm as I would want to change the chain and tensioner whilst I'm there so it will all start to come to some money. I'm currently at 50k miles - will think about it when I hit 60k...have been spending a lot of money recently on other upgrades and fixes.

[Grande]

A sound like the first one is one not to worry about as it doesn't do any harm (other than making the horrible noise).
If it is the first one you will find it happens more frequently in the winter (colder weather). It will also happen more as you get closer to your annual oil change.

Have you thought about trying this DIY fix for the camshaft adjuster?

http://www.vwwatercooled.com.au/forums/ ... post805063

It was also posted on this forum somewhere but I've never seen anyone confirm that it works.

Mine just started making the same tractor noise again as it got colder.

Cold start poor running for 30 seconds or so, making a burbling/popping noise from the exhaust and somewhat rough running (can feel shimmers in the cabin)

Caused by ECU software glitch during pre-cat heating on a cold start.

Is there a way to tell apart the glitch and a normal cold start? Seems to be the same thing.

[froudeg]

I tried that - made no real difference, it stopped it doing it for a day or 2 but then it started sticking frequently again.
It was RW1 who came up with the idea, you can see his original post here:

http://www.sciroccocentral.co.uk/forum/ ... 25&t=11007

I believe that the oil flush and change he did shortly after cleaning/pulsing the solenoid is what alleviated his issues with the camshaft adjuster sticking.
The intermediate oil change and flush every 20k is what keeps mine at bay, but it still happens once in a while but can go months without it doing it now.

[Grande]

Oh well, another annoyance to live with then. So anticlimactic when you get in and it starts like a tractor

I park my car in a deep underground garage where the temperature is just above 19 C during summer and just below 19 C during winter. It doesn't make that noise when I start it from there.

However, I have noticed that during summer it always enters the 30 second cold start sequence and during winter it doesn't! It's funny because it's the opposite of what you'd expect. So, you're saying that is a glitch?

[Cuprabob]

Depending on a number of parameters, on cold start, the Secondary Air Injection (SAI) is activated for a period which sounds louder than normal and while running, the idle speed is raised.

[froudeg]

There is no secondary air injection system on this engine, other than high idle for 30 seconds or so, this differs from the temperature related quirk of very rough idle for 30 seconds

However, I have noticed that during summer it always enters the 30 second cold start sequence and during winter it doesn't! It's funny because it's the opposite of what you'd expect. So, you're saying that is a glitch?

Yep its a glitch there is no reason I can think of for it to be misfiring, run rough with the incorrect fuel levels only between a coolant temp of roughly 19c to 32c.
It's just another little quirk with the ecu firmware on this engine.
VW have released many revisions to fix so many issues on this engine over the years, one of them was to fix this very issue but they never did properly fix it.

When it does actually do the cat preheating on a true cold (winter) start it doesn't misfire and burble like crazy like it does with the above conditions.

[Grande]

When it does actually do the cat preheating on a true cold (winter) start it doesn't misfire and burble like crazy like it does with the above conditions.

Personally, I haven't noticed a difference (and I'm very familiar with it, because I have a habit of sitting through all of them from start to finish ). But maybe you're right.

In any case, I'm going with emissions / fuel economy test rigging The test probably requires a coolant temp of 20 C or so and a half a minute of idling before putting on the dyno. This way the engine warms up quicker! (I'm joking of course! Or am I? ).

[froudeg]

lol! - you would think it was a joke...but hell who knows what those little software engineers were up to - I wouldn't put it past them!