S3 Spluttering/Misfire When Cold

johal87

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Hi guys,

S3s been acting funny, video attached, only when cold, and doesn't miss if you rev. Only faults that come up were cylinder 2 misfire which I've changed the coil pack, and knock sensor. Also can be a but smokey? And smells like it's running rich?

 
Checked the spark plug? Worth checking your coilpack harness to as the wires may be corroded
 
wont the rich smell be because it is passing through a load of fuel from cylinder 2.

with my car someone replaced the coil pack but the spark plug was the real problem and actually knackered the new coil pack maybe due to arc'ing as the ceramic was half missing, had a similar problem on a Mercedes c200 where the coil pack is changed rather than the extra 30 seconds to check the spark plug.
 
If not simply changing the plugs why not move 2 to 1 and coil 2 to 3? And see whether the fault moves?
 
plugs and coils have made no difference..

Also I know a knock sensors gone as the car knocks from time to time, but my like a idiot erased the scan before jotting down which one and now I can't get it too come back up!

Any advise on the misfire?
 
I did read an article about an "amplifier" somewhere on the airbox - but the common misfire issue was cylinder 3 not 2 - might be worth a search?
 
I did read an article about an "amplifier" somewhere on the airbox - but the common misfire issue was cylinder 3 not 2 - might be worth a search?
Ignition amplifier is on AGU engines only I believe, which you won't find (originally) in an S3.
If you have push-down coilpacks, you don't have an ignition amp.
 
Check your harness to the coilpacks.

what exactly will I be looking for? Breaks in the wiring? the plug for the actual coil pack is broken, it fits and is tight, but it can just be pulled off..
 
did you break the tab off trying to change the coil pack or was it already broken? 2 of the 4 tabs of mine are broken but that is not a problem for me they are still in tight enough. my earth wire is in a sorry state that is a common heat related issue, I assume all your wires are still tucked up safe in the heat wrap under the charge pipe?

just weird it only happens at idle, you would think if it was electric related it would get worse under load rather than improve, I assume there is no coolant disappearing slowly into the cyclinder head, or feeling of high pressure on the water hoses?
 
yeah it was already broken, I wouldnt mind changing the section of loom if its not too hard and possible? Yeah all wiring seems good, but I will have to double check it, might move the bits and pieces out the car and see if theres anything not quite right.

Coolant level hasn't dropped, and oil seems fine also, i did buy the car knowing this issue, and done roughly 200 miles in it since, it drives as you would expect, and only misses when cold, also noticed the temperature needle doesn't really move, sometimes it does, other times its dead, do you think this would be down to the dash pod? or possibly a sensor? VCDS has no errors on a temp or coolant sensor..

all the bits are starting to annoy me now, as it was meant to just be a project to sort over a few weeks, get it prepped and have a nice reliable winter runner...

I've brought a full set of bosch super 4's and a new oil filter to have done on the weekend as well, but now I'm more than likely going to leave doing that until I can get it running right, also think its in my best interests to clean the oil up pipe as I doubts its ever been done, picked up 20LT of triple qx c3 5w30 oil for £48 at eurocarparts as well which will see her for 4 services hopefully
 
I would change the plugs straight away if it is misfiring. they are the cheapest starting point. but I am not expert, but you have moved the plugs and the coils around and still cylinder 2 is misfiring?

my Punto was misfiring showing 6 or 7 errors all because the speed sensor was shot.