Lumpy cold start

PhantomBlackS3

PhantomBlackS3

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hi all, back with a new problem added to my long list lol.
Recently...more like the past couple months I've noticed that when i start my car its lumpy on cold start initially but any start after that is fine unless its left to completely cool down.
Had the car plugged in to VCDS and absolutely no codes shown whatsoever.
Initially assumed it was a problem with the RNS-E unit constantly spinning the nav disc which i could clearly hear when the car was turned off, the sound of the laser reading the disc was very distinct, also been told it could be the fan for the unit failing which is spinning constantly.
Since removed the nav disc and it still starts lumpy, i should note the car is used little to not at all, maybe once a week if not maybe once every ten days.
Trips are usually short as well, its driven spiritedly but nowhere near to the extent of some S3 owners, i don't push the car to anywhere near its limits.
Anyone ever experienced this issue before and can shed any light? The no codes part is really throwing me, the only other thing i could think of is the battery losing charge and struggling to turn the engine over on the first startup.
As always any help is appreciated.
 



I’ve provided a video i took on one of the occasions.
It usually doesn't get much worse sounding than this and always starts every time but im almost certain it shouldn't ever sound like that.
 
Lack of use doesn’t help. It’s a direct injection engine so all these cold starts (which inject extra fuel each start) will produce a build up of soot on the inlet valve stems and inlet chamber. The more mileage on the car the worse it gets.
Many of the forum members have had clean up of the valves either by removing the inlet manifold and manually scraping the gunk off or a having walnut shell blasting by a garage that have this facility.
High mileage injectors can loose their spray pattern and cause rough idle.
Vacuum pipe leaks is another cause.
All of the above will not show up a fault code and why I suggest the known problems.
 
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The battery and alternator can be easily checked with a voltmeter, if you have one.

I recently had a problem with "lumpy" starts which was down to a timing issue. It also did not throw up any codes.
 
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JayTeeA38P said:
The battery and alternator can be easily checked with a voltmeter, if you have one.

I recently had a problem with "lumpy" starts which was down to a timing issue. It also did not throw up any codes.
Click to expand...
Apologise for the late reply, it seems the problems for my car reach farther than a lumpy cold start, i not have an EML on and it sounds like im down a cylinder the way the engine is chugging. Few people have pointed to an injector but i’ll post up as soon as i have a solution, it seems my S3 is cursed, so dare i say it the end of my audi days are nearing. Fancy a BMW or perhaps a nice Mk7 golf GTI.
 
Stupid question alert…have you checked coil packs
 
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Something similar here, rough idle only on first cold start without any fault codes. I also suspect on soot on the inlet valve stems. Unfortunatelly in my country I can not find garage for valve cleaning with walnut shell blasting but I have idea to try DIY cleaning with liqui moly valve cleaner directly through inlet manifold and after that to drive one hour italian tuneup on highway. Ofc I can not expect anything spectacular but that is the best liquid cleaner I can buy here for this purpose and try to clean anything inside. I'm worried just about turbo if large chunk fell out and damage something. :sadlike:
 
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Whatever car you end up buying will have the same problems later on. It’s the lack of use that’s causing a problem.
 
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SootySport said:
Whatever car you end up buying will have the same problems later on. It’s the lack of use that’s causing a problem.
Click to expand...
Ive just recently had an injector fail on me, the car is in my mates garage getting fixed as we speak. He's went over the engine with a tooth comb and found no sign of any other issues...I'm not saying thats been the cause of the lumpy start but i had misfiring issues at the start of the year which was actually the reason my coils and plugs were changed in the first place, dv revision G was fitted, pcv valve and cam follower all replace..all that for the injector to go, i coulda been sick when i found out. But as you say more use should aid in a smoother running car?
 
doce said:
Something similar here, rough idle only on first cold start without any fault codes. I also suspect on soot on the inlet valve stems. Unfortunatelly in my country I can not find garage for valve cleaning with walnut shell blasting but I have idea to try DIY cleaning with liqui moly valve cleaner directly through inlet manifold and after that to drive one hour italian tuneup on highway. Ofc I can not expect anything spectacular but that is the best liquid cleaner I can buy here for this purpose and try to clean anything inside. I'm worried just about turbo if large chunk fell out and damage something. :sadlike:
Click to expand...
Have you thought about giving it a go yourself with maybe a friend who's got a bit of knowledge with engines? Ive read up on getting the intake cleans and i personally was going to attempt it myself but it woulda been over a far longer time than it would take a mechanic.
 
PhantomBlackS3 said:
Have you thought about giving it a go yourself with maybe a friend who's got a bit of knowledge with engines? Ive read up on getting the intake cleans and i personally was going to attempt it myself but it woulda been over a far longer time than it would take a mechanic.
Click to expand...

I've done it last night with liqui moly valve cleaner without inlet manifold disassembly. I sprayed liquid cleaner through second map sensor hole just above inlet manifold. The procedure took 15 minutes with the help of friend. This morning on the first cold start no more rough idle but I probably removed no more than 20% of carbon. I plan to repeat this procedure again in 2 weeks and find some boroscope to check the condition.

The procedure I used on my 1.4 tfsi:
  1. Warm up the engine
  2. Turn off the car and remove second map sensor just above inlet manifold
  3. Start the car, hold engine at 2000 rpm's and spray through the map sensor hole in short bursts until can is empty
  4. Turn off the car, connect map sensor and allow engine to heat soak for 1 hour
  5. Drive at highway speeds for 15 minutes
After this procedure CEL pop up because I removed map sensor. I had to remove fault codes and after that, the light remained off. Also we had a real smoke show and pretty large black spot of carbon on the back of car. I do not have a catalytic converter on the car so I'm not worried about that part. :happy:
 
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