# Cold start hesitation - TFSI



## lordlee (Jun 20, 2012)

Hi All,
I have experienced a slight hesitation first thing on cold start this week. It's literally for the first mile and then it's gone. No there running problems at all. I changed the coolant temp sensor just for fun but it's made no difference. Anyone had anything similar please?


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## lordlee (Jun 20, 2012)

Anyone?
I just can't think what would only show on cold start but not really on the rest of the cycle? Maybe it's just exasperated on the cold start cycle.


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## SamoaChris (Jun 24, 2014)

I wouldn't be very happy either! :roll:


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## Sophus (Apr 26, 2013)

Not really, but in general the usual recommendations are to check or change spark plugs, make sure fuel is good quality, check PCV valve, if you have VCDS you do a throttle body alignment. A weak or intermittent coil may be the case. Check and if necessary clean intake if much buildup of oil and carbon. I'm sure there are more things to check, these are just a few.


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## lordlee (Jun 20, 2012)

I recently changed all the plugs but for the ones with 6 in rather than seven as the car was getting remapped - but it ran OK when I fitted them ahead of the remap. I've tested the pcv valve as far as removing the dipstick and the engine running rough - I don't know how better to check it. I've run vcds but there is nothing specific showing up?


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## jocco (Apr 6, 2015)

I had a similar problem trough entire winter on my 2006 TFSI.

When I start the car in the morning the auto-choke starts to engage and immediately drops the revs to 900RPM.

And the car would basically run with no choke on cold start, also on the first touch of the throttle I could hear a small pop from the exhaust.

This would happen for a minute or two, the the car would run fine. Once warmed up I had no issues on startup until the next morning.

Now that the weather is improving the problem is gone.

I tried all the things Sophus mentioned to no avail. Changed spurk plugs, still nothing.

I'm running a BSH intake however, was planning to go back to the stock box, but then as I said the outside temps are up, and now there is no problem.

If you get it sorted, let us know.


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## ttrev21 (Jan 30, 2009)

I have a very similar problem on my TTS

Missfires when cold for about 40 seconds then the revs drop to 900 and ticks over fine

Also worse in the winter than summer, diagnostics show a miss fire on cylinder two but it very rarely logs it?
So far I have thrown at it four new plugs, then four new coil packs to no avail
Then replaced the cold start sensor which seems to have improved it although not cured it

Audi are now saying resistance test accross wiring or possible leaky injector but they cannot promise it will cure it even if they try??

So currently undecided how much more money to throw at it, so will be watching this thread with great interest

Driving me nuts :evil: :evil: :evil:


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## lordlee (Jun 20, 2012)

A mate has a set of high performance coils so I'm going to start there and see how it goes. I'll report on my progress throughout this journey...


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## jocco (Apr 6, 2015)

Funny thing is I had a Seat Leon 2.0 TFSI with the same BWA engine before the TT, and that also had cold start issues, which were worse then on the Audi. 
I had to crank the car two times every morning in winter. 
I sold it before I got to the bottom of it.

Sent from my iPhone using Tapatalk


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## lordlee (Jun 20, 2012)

I have had the performance coils fitted today (the car has its original coils in it which is pretty amazing) but the cold start will come tomorrow morning. 
Interestingly we noticed that a rubber bung from the engine cover was stuck on its peg which effectively was creating a vacuum leak - it pays to make sure you remove and replace all bungs before refitting the cover to make sure you don't have this issue.
Looking forward to starting the car in the morning to see where we're at...


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## TT-driver (Sep 14, 2010)

lordlee said:


> Interestingly we noticed that a rubber bung from the engine cover was stuck on its peg which effectively was creating a vacuum leak - it pays to make sure you remove and replace all bungs before refitting the cover to make sure you don't have this issue


I believe the rubber bung issue won't create a vacuum issue. It merely causes the engine to also draw air from the inside of the engine bay, rather than just the stock cold air intake.

The choke concept..... doesn't exist any more. The engine management injects additional fuel just after start up in order to heat up the catalytic converter as fast as possible. Once that one is heated up, the engine management switches to 'closed loop' mode. In closed loop the exhaust gases are examined by the lamba sensors. What ever is wrong with the mixture is then adjusted for by engine management. Only during full throttle the engine will go back to 'open loop' -> rich mixture for maximum power. 
When it's cold, the open loop mode after start up may last up to a minute or even longer. During that period the exhaust sounds a bit as if it has a leak. This all is perfectly normal.

Installing colder plugs may result in carbon build up on these plugs. Carbon deposits may cause misfires. So it's important to check if these colder plugs still reach the self cleaning temperature. If not, spark quality will deteriorate.


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## lordlee (Jun 20, 2012)

Thank you for your reply. The plugs are very widely used across many TFSI applications so I'm happy it's not them. It's just in the very early cycle - I'm really hoping it's coils as that would be very easy to rectify.


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## Hardrhino (Apr 30, 2009)

Fingers crossed for you but as above TTrev21 has changed plugs and coils to no avail...

How did it go this morning?


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## lordlee (Jun 20, 2012)

Great news - started like a dream today and runs beautifully smoothly. Seems it was just the coils. I have to give these nice ones back now though :-(

I looked at the R8 ones http://samtechperformance.co.uk/presta/ ... er=product (available from Awesome GTI too) and these look good. Anybody used these or got a better set they can recommend please? The budget looks about right on these I have to say.


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## TT-driver (Sep 14, 2010)

Glad it is fixed


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## lordlee (Jun 20, 2012)

TT-driver said:


> Glad it is fixed


Thanks - I was pretty much expecting it was going to be one of those nightmare hard to trace faults so coils are a bonus.


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## BlueMagic (Feb 14, 2015)

lordlee said:


> TT-driver said:
> 
> 
> > Glad it is fixed
> ...


How many miles had the car done?


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## lordlee (Jun 20, 2012)

It's done about 90k so the original coils held up miraculously well.


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